Not quite true.
Original 85D acceleration was 0-60 in 5.4 sec (this was probably also underrated).
On a point release after 6.2 (that I don't recall) they added a Sport mode to the 85D that made it 0-60 in 4.4 sec (again still underated).
Another subsequent release removed the Sport mode and made the 85D always be 0-60 in 4.4 sec.
It's been generally observed that you can do better than 4.4 sec in the 85D some saying as low as 3.9 sec.
It's not clear if the reduced time is a further hardware improvement on newer cars, a software improvement, or no improvement and Tesla just adjusting the number to be more realistic.
Time and testing will likely answer that.