Why and how the text could be Bavarian

[ololololo]

Let’s ask it the other way around: What other theory can achieve all this with so few assumptions?

If you number the letters with Roman numerals and turn the words into anagrams in order from largest to smallest, the result was similar to the VMS text (there will be doublets, triplets, and "words" that are similar to each other). If you choose the alphabet correctly, I believe you can get as close to Voynichese as possible on your first attempt.
This doesn't apply to your theory, but in my opinion, it's easier to do...