Interesting, I didn’t know that. I suspect many casual observers don’t either. So you’re suggesting they did this work with proprietary info they’d gained through work with Sega and thus broke their NDA?
Funnily enough, one of the most famous Generations mods is a project that ports over a bunch of levels from Unleashed. IIRC they changes the graphics pipeline to look and work more like the Unleashed one, too.