Let's imagine that all the driving instructors in the world dropped dead and we had to learn to drive from books.
Now let's say someone selected the shortest book with the most obscure information, like the notes used by a driving instructor. Let's say that they then rigidly followed the specific examples of driving outlined in those notes. Let's also say they practiced only on a straight section of road and it worked more or less in this situation. Would you get in a car and be driven around with that person? Hell no.
Now let's say someone else read and compared many different books on driving. They had a primary book, a good book with lots of information, but they had read many other books to see if there were gaps or to expand up areas glossed in their chosen book. They'd thought about why people did things (held their hands differently on the wheel, or used different feet on the pedals) and focused on understanding why they did this, not just on how. Let's say they thoughtfully made logical and practical conclusions about how to apply the examples to different situations and had developed a robust understanding for various situations. Would you get in a car with this person? Sure, though I might watch them driving around first before I did.
Anyhow this is how I feel about the study of HEMA. Arguments about the "right way" to do a Krumphau is akin to arguing endlessly about where to hold your hands on the wheel or exactly how hard to pump the brake. Limiting your practice to exactly to the examples in the treatises is like never taking a third right off a roundabout because that specific example never came up in your book.
Finally if the argument was to keep the study "pure" to produce an "authentic style" of driving you would have to ask yourself: what does it matter how pure your style if you cannot drive? Does it matter what's the authentic way to hold the wheel or the authentic way to pump the brake if you keep coming off on the first bend? No. Once you've understood about corners then how to turn the wheel and how to pump the break will take care of themselves. Once you can drive then you can try taking the corner with one hand on the wheel and the other hanging out the window.