I think it’s just tongue in cheek, Mike. Nobody thinks they’re getting away with anything, nor is anyone really advocating copyright infringement, it’s just a way of saying “close-as-makes-no-difference.”
I mean I’d love for GW to produce and support a 3mm scale Epic line. And if I had a Rolls Royce Phantom-II, I’d polish and wax it every day. But it ain’t gonna happen. So to distinguish my own project from something officially sanctioned that it is nevertheless pretending to be, I refer to them as my “Not-Space Marines.” It’s not that I’m trying to fool anyone or get away with anything, I’m just doing my own thing.