Isn't that because most of their vehicles are supposed to be recycled from the RA1 era? That, and the whole "RA2 never happened" thing.
Also, if you're talking about the Nazis, then I don't think using German tanks automatically equals Nazi endorsement or something. Especially in a universe where the Nazis aren't even a thing. (And the RA1 medium tank was an M1 Abrams of all things, so they obviously can't just use that.)
Not directly. the insinuations are more in how the mastiff was hyped all across paradox lore. start to look and you'll notice a trend. but yeah most of their equipment was supposed to be R A 1 throwbacks. still, could've been a bit less parralel probably.