I want to second this and I would love to see this get more attention from other players
It's also impossible for the game to register the input for the late flip while going into a grind from flat ground.
I was trying to replicate a P-Rod trick— Nollie, late kickflip, nose grind on a ledge. The game doesn't even register the input for the late flip while going into a grind. However, this is something I was able to replicate in previous skate titles.
I think that they are one in the same issue and improving the late flip timing would go a long way to improve realism