In recent versions, Experience Bottles, Splash Potions, Snowballs, Eggs, and Ender Pearls now land 1 block short of expected location

This is what throwing an Experience Bottle looks like in 1.20.6, landing on the 7th block (red sand):

This is what throwing an Experience Bottle looks like in 1.21.4-pre3, landing on the 6th block (water):

(^^ The same applies for Splash Potions too ^^)

I also conducted some tests with Ender Pearls, which yielded:

Num. blocks covered / 1.20.6 / Ender Pearls
13.6
14.8
16.3
14.8
11.9
12.1
14.8

Num. blocks covered / 1.21.4-pre3 / Ender Pearls
13
13.2
13.4
13.3
13.4
14.7
13.3

Setup used for Experience Bottles & Splash Potions:

Setup used for Ender Pearls:

The player is teleported/centered exactly in place by using /tp @s x.5 y z.5 0 0