You'll note I'm not reinventing things, most of this project is connecting dots between open science and already amazing projects like iNaturalist. But if you're familiar with it, you might also be frustrated with its extremely simplistic approach to identifying natives.
The reason I suspect is why your last point exists, except I've spent an inordinate amount of time and effort ensuring that Indigene doesn't claim a plant is native to a region (vs. a whole continent) when it's not. That makes it less comprehensive than other resources, but unless you can point to specific issues it doesn't make it less reliable.
I can't make you care, but if you might this is where I'd look if I were skeptical:
https://indigene.app/confidence
https://github.com/olivierlacan/indigene/blob/main/DATA_SOUR...
https://indigene.app/plants/penstemon-digitalis (example of a status conflict)
https://github.com/olivierlacan/indigene/blob/main/app/scrip... (which is what does this status checek)
And if you care to call me out on any GIS mistakes (given my own lack of expertise in that area) this where you're likely to find mistakes: https://github.com/olivierlacan/indigene/blob/main/app/scrip...