Whilst that certainly holds up in terms of internal logic, it's a bit unfortunate that you've just reasoned yourself out of a job and condemned the activity of writing by hand as futile.
All letters 'a' for example should look the same or as close as possible to every other 'a' in the text. In this regard, the best mechanically-produced fonts which appear to have been handwritten, are at a distinct advantage. The best of these are truly beautiful.
No matter how hard I try, I will never be able to copy these letters consistently and exactly. However, on a good day, I can get pretty close. This is my objective, and I derive a great deal of pleasure in the act of writing. Having been hand- produced, my efforts will inevitably contain many inconsistencies and its those variations which have their appeal as having been produced by a human and it's this alternative to mechanisation which makes calligraphy an attractive option to clients.
I have held this view and approach to Calligraphy all my life. I worked as a part-time calligrapher from 1963 until 1986 when I went full-time. For the past 30 years, I have never been out of work, and at the age of 77 I'm still working full-time although I can now pick and choose my commissions.
I have hardly "reasoned myself out of a job" and I certainly don't consider "the activity of writing by hand as futile".