That's a great question and I agree it sounds like it would conflict big time. However, it need not if certain things are borne in mind. What I mean is that one must remember what is more fundamental or foundational and what is entirely secondary to a process of discernment and formation. Above all, the kind of book you describe should not attempt to define or drive the necessary process of discernment and formation of a hermit petitioning for c 603 standing, though it may well be used to mark and document points within the process after they have been achieved or negotiated. For instance, some dioceses have chosen to use The Catholic Formulary, vol 7A by Rev. Peter Apkoghiran, JCD, a book whose clearly stated purpose is [[to guide church officials in drawing up ecclesiastical public documents (and) also ensuring that such documents fulfill the solemnities and requirements of canon law.]] This one is on my mind first because when I read it a year or so ago and saw it as a classically flawed attempt to do more than the canonist could or should do in such a book, and more than the stated purpose. It is also on my mind because (apart from your question) I heard more recently about a diocese using it or thinking of using it for c 603 hermits.
What the book is not meant to do, and I submit, would be well beyond its purview, is to define the structure, content, and time frame of a discernment and formation process or program under c 603. Were a diocese to adopt the process I have outlined here which is focused on writing various Rules of Life to guide discernment and formation until one had a liveable Rule which truly indicated the hermit's lived experience AND reflected the contents of c.603 and had the formation team worked with the candidate to achieve this, the Formulary could be used to "formalize" with canonical documents various steps along the way. However, what is especially important is that it must be the process of discernment and formation that drives matters, not the documents, much less some arbitrary time frame -- even if that time frame works well for coenobitical religious!!! Neither would the hermit be shooting towards achieving what the documents measure or mark, but rather simply towards becoming what God calls her to in terms of canon 603 itself.
Some people see c 603 as inadequate to govern solitary eremitical vocations. After all it doesn't list time frames, or ages, or all kinds of things canonists find necessary or desirable. Non-hermits look at the canon and often find it equally inadequate because it is not a "how to" guide to what is necessary to becoming a hermit, much less a canonical hermit! But c 603 does precisely what it was meant to do, namely, it provides the central non-negotiable elements constituting a solitary eremitical vocation and in sec 2, provides the way it is to be lived out as an ecclesial vocation. It shows us what such a vocation looks like and what the hermit commits herself to living in the name of the Church. I would argue that if one finds the canon inadequate in major ways, they have only understood it in a superficial sense.As a reminder, the process I have outlined here over the years grows organically out of the canon itself. It is more fundamental (foundational) than the canonical documents provided in The Formulary. The Formulary thus can be useful, but the moment it supplants the actual process of coming to write a liveable Rule of Life as c 603 requires, it becomes destructive. Unfortunately, because human beings are tempted to replace Gospel with law (sometimes this is the simple expedient), and too to multiply law to deal with perceived insufficiencies, canonists and other diocesan officials are tempted to add to canon 603, or to shoehorn it into an alien framework, instead of first understanding how the discernment and formation of hermits actually looks on the ground. In such cases they more often end up with lone individuals who can jump through canonical hoops but will never be a hermit formed in the silence of solitude by the Holy Spirit. When that happens c 603 becomes incredible and the work of those who composed the canon will be eviscerated.
Hermits who really understand and live c 603 will be highly disciplined, on the other hand, and far more likely to be allergic to such hoop jumping! They may seek to be professed under c 603 and be an excellent example of solitary eremitical life lived as an ecclesial vocation --- but if The Formulary type of text with all its artificial stages, etc., is imposed needlessly, these vocations are more apt to be lost to the Church. What I am saying to you is the The Formulary and texts like it create documents which may be appropriate to formalize a truly foundational process of discernment and formation rooted in c 603 itself, but the documentation is not meant (and should not be used) to create or define ahead of time a process of discernment and formation. The two elements (process and canonical documents or form) absolutely need not conflict "big time", as you put it, so long as one does not put the cart before the horse!!! Again, what is most fundamental is the canon and the process which derives directly and indirectly from c 603 itself, namely, the requirement that the would-be canonical hermit write a (liveable!) Rule of Life of c 603 based in her own lived experience of eremitical life.In other words, the process deriving organically from c 603 itself should drive matters, not the documents canonists determine to be important for other (and secondary, though important) reasons. And yet, letting the documents drive matters is the danger of using a text like the Formulary if one does not already have a sense of what c 603 itself requires of an individual in terms of personal growth and maturation as a hermit. Adopting something like The Formulary without a clear and appropriate process, which is truly organically derived from the canon itself, being treated as more foundational is deceptive and self-defeating. I should also note that unless it is made clear at every turn that The Formulary is secondary to the canon itself with all that implies in terms of learning to live it ever more-deeply, there is an ever-present danger that dioceses seeking information on how to proceed with candidates for c 603, will take hold of The Formulary and leave the less concrete and far more fundamental discernment and formation process behind.