Yes, I wrote that just recently and I have done so from time to time over the past fourteen years as well. There are always exceptions of course, but generally speaking, most people showing up seeking to be professed as diocesan hermits have never lived in the silence of eremitical solitude at all much less for an extended period of time. If you were to engage them in a conversation on canon 603, its central elements, history, or the vows it calls for, you would find they knew little if anything about these. If you asked them to describe the vision of life they live by few would be able to articulate this, and if you asked how it is they structure their lives in light of their life in and with Christ, the response you would get is a far cry from what eremitical life looks like.
In those I have been in touch with, it has seemed to me that a number of them are expecting the diocese to accept them as candidates in some sort of hermit formation program and to profess them at the end of two or three years after they have simplified their lives a bit, been kitted out in a habit, and read a few books about prayer, desert spirituality, and the vows (maybe!)! In truth, those who are serious about eremitical life are at the beginning of a long journey, a life-long journey, in fact, which will change them to their roots -- just as it will reveal God to them in ways they could never have imagined. It is only as a person has lived this journey for some time, and have begun to glean a vision of what its shape and substance will be, that they will be able to write a liveable Rule of life.
So, no, I do not suggest that dioceses have people live as hermits for a few years before asking them to write a Rule in order to draw out the process or set arbitrary obstacles for the person. The process is an organic one which takes work, and prayer, and time --- significant periods of time. Dioceses that ask someone to write a rule as soon as they believe the person might be a suitable candidate for profession does this person no kindness. Instead they can be setting the person up for failure. Using the gradual crafting of a liveable Rule as a guide to discernment and assistance in formation simply makes good sense and takes advantage of what the process demands anyway. In any case, I suggested what I did because I want to see people succeed in what is already a demanding process. I want the Holy Spirit to be given a chance to work in all the ways She needs to work. My own writing of my Rule was, until the past four years of intensive inner work, the most formative experience of my life. I very much want others to have a similarly rich and fruitful experience if that is the will of God --- and yes, I absolutely want to educate dioceses on the way the requirement that a hermit write her own Rule can be allowed to be a grace for all involved!!!
Do I think I know more than dioceses do in this matter? Yes, generally speaking, I believe I do. I have learned from my own crafting of a Rule and I have sometimes mentored others. Thus, I did not impose a set process on anyone, but I urged them to allow the Rule to take shape as their own eremitical lives and corresponding vision did. Those who were able to entrust themselves to the potter's hands over what was typically a several year period, evidenced a similar process to my own. We each made the journey and allowed the journey to shape the Rule just as we allowed the portions of the Rule we had composed (and therefore, canon 603 itself) to further shape and define our journeys/lives. This is not arrogance. It is humility -- a loving honesty learned by trusting the Holy Spirit and the call we each heard or discerned in the other, a humility meant to assist dioceses and those faced with the prospect of writing a Rule of life despite never even having read, much less lived according to a Rule! (My friend was very far ahead of the game in this regard and yet, her own growth and inspired vision took time to form and more time to come to expression in a liveable Rule!!!)
I know that this requirement of canon 603 is the most concrete-sounding element of canon 603, and the most easily pinned down by a diocese with little experience or sense of how to proceed in this matter. But it is not one someone without experience living solitary eremitical life can accomplish --- nor should they be asked to try, especially without mentoring. A Rule is a tool, but it can become a precious friend --- if I may speak this way --- for the Rule accompanies us, supports, challenges, inspires, guides, instructs us, and protects our vocation. It is a window for the Holy Spirit, a living document which breathes with the life of the hermit, her Abba, and her Lord and Spouse. It (and certainly the crafting or weaving of such a sacred text [from the Latin texere, to weave]) should be allowed to function in all the ways such a process can function. This will serve the hermit, the diocesan staff who work with her, the Church universal who promulgated canon 603, and the eremitical tradition entrusted to all of these.