Perhaps not snake oil.
In 1990 I spoke with Dan Healy before the Grateful Dead show at Sandstone, and he was lamenting that there had not been a real advance in speaker technology in many years.
Graphene drivers (and for that matter graphene dynamic mic diaphragms) would not be a bad idea, though it might not be revolutionary.
Remember how the use of "Rare Earth" magnets allowed Sony to increase output and decrease size and weight of their headphones in the early '80's and the Walkman became a thing!?
I see that one point touted for the Graphene products is that the lighter materials will improve battery life (energy efficiency) - That's hip.