Interchangeable ch/sh and k/t characters

[ololololo]

Example in German: Ein/eine, Bein/Beine, sein/seine, mein/meine, dein/deine, kein/keine, … etc.

An interesting example. But in the case of Voynichese, we have pairs of letters that can be replaced. According to the example, I can replace any letter from any word with any other letter, and it will also make a meaningful word, but this is not the case: there is no word aaiin in the manuscript, there is no word fkshy, etc.
It is also necessary to take into account the specifics of Voynichese. As much as we would like to, it's not just German