Very well stated summary of my position.
It is ok to train other "wing chun", whether it derived from YM and was changed for whatever reason, or whether it came from somewhere else, for example recreation from scratch via old texts and imagination. But there is only one VT system that YM taught and that works in the way it was designed to work. Saying that all of the different approaches are equally valid interpretations of the same system is not true. Changing the system changes the system. The result is no longer the system, but something else. If you prefer that other thing then it is no problem to me.
Spoken like a true "VT snob."