There are gaming keyboards with 1000hz poll rates.
For a better test, in my opinion, the key actuation point should be determined and the timer started at that point. Of course this depends on what you want to test. But to say that a gaming keyboard is slow, just because there is more key travel, is inaccurate.
this would be like saying a physical kick drum or high hat is laggy, because theres a delay between when your foot starts moving and when the sound happens. (which would be silly!)
Or maybe there is some optimal separation a key should have between the actuation point the tactile click point to account for the latency of the human's nervous system, which would do an even better job of reducing the effects of latency than if the two events were at the same point?