This is very much still an issue in 1.21.100
There is a very noticeable ~0.25 second delay when doing any action, even in singleplayer
This is most noticeable when shooting a bow or reflecting a Ghast fireball
To reproduce: shoot a bow a couple of times in Bedrock. Try shooting phantoms, ghasts, etc.
Then compare to Java edition (which has no delay)
It seems like there's some kind of client-server communication that occurs before the arrow is released where on Java the client owns the arrow they shoot
On Java edition, ghast spawns have a 95% chance to fail
That failure chance is not present on Bedrock, but they still have a similar spawn rate