Of course it's a trademark, but it's a trademark of a particular product they offer.
Because the Powergrip HTD is a fibreglass belt and therefore, inferior to a kevlar braced belt. That's why.
Why not put the Powergrip GT logo on it? Or Powergrip GT2? Those are also trademarks owned by Gates and the GT2 is actually a kevlar reinforced belt.
It's really academic, I think. I'll just call the Gates rep. :-)