Adding caching to Prettier is reasonably easy, and most people will already have it through lint-staged or something similar.
I'm much more impressed by "dprint is 3* faster than Prettier for the same task" than "dprint is 40* faster than Prettier because dprint caches results and Prettier doesn't". That makes me want to look at dprint. The "40* faster" figure makes it look like the benchmark is wrong.