I don't know what the process for getting stuff on Steam Workshop is. I guess in theory people have to test for compatibility? But if it's like Early Access, Steam won't do a thing.
I don't think it's a problem with the models, if I had to guess I'd say doing it via the Workshop might prevent Steam from altering files needed for those mods to run?
Maybe? I have no idea, I don't use Steam. As I recall, it does involve some decent fiddling with one of the 2da files to make sure it doesn't break every other mod ever.