I checked survey of 2016 where his data show, 2900 bullet in chess.com = 2700 bullet in lichess= 2500+ Fide. So hilarious. There are more than 10 thousands of GM ( I guess) and only a few dozens/hundreds ever crossed 2900+ in bullet.
So wrong.
Possibly he got some data from some trolls.
If his data is correct, every GM would be 2900 + in bullet.
It is fairly accurate in my experience once you are in the middle range. If you want a concrete answer then just see the first ten of the titled players chess.com says are online now and view their stats compared to their actual otb ratings to come up with a differential. Usually they are fairly close for blitz, a bit less close for bullet, and least similar for the other time controls.
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How close are Chess.com ratings compared to USCF OTB ratings?