They're not "graphene" particles, even though I called them that in the OP (didn't want to be too harsh). They're tiny graphite particles, WAY, WAY, WAY cheaper than actual graphene and also cheaper than a good carbon pre-preg. So it is NOT graphene lol; I don't know why I keep repeating it is not graphene and you choose to ignore it. Per your argument, if a purported material makes the racquet feel different then it isn't a gimmick. So I can sandwich some plastic into my racquet, sprinkle in a little diamond dust, and say the new racquet is diamond-reinforced awesomeness. Sure it may play a little differently, but isn't that kind of marketing disrespecting and under-representing the real properties of diamond, and hence a gimmick? And nomenclature is incredibly important. Materials of slightly different names can have completely different properties.
I call it graphene because Head calls it graphene, players at my club call it graphene, literally 99.999% of the world calls it graphene. You seem to be the only one who is obsessed with getting the correct name right and calling it "tiny graphite nanoparticles tm". Like I said, borderline paranoid smh.
and YES, if you have an R&D department and find that sprinking diamond dust makes a racquet have completely different playing capabilities you are allowed to say it is diamond-reinforced, the next new innovation in racquet technology, etc. you can say whatever you want, that's the point of marketing and the reason why thousands of people have jobs. But as long as it works as intended it's not a gimmick, despite your best efforts to disprove that.
A true example of a marketing gimmick is putting flame decals on a racquet and stating "Now allowing you to swing faster than ever!!!" No, it won't change a thing (unlike the addition of graphene to racquets).