Soul sand collision box incorrect

Soulsand is meant to have a slightly shorter collision box than solid blocks, which allows entities to sink into it. This is no longer the case.

How to reproduce:

1. Place any solid block and one soulsand next to it.
2. Walk from the solid block onto the soulsand.

Expected outcome:
There is a noticeable dip and the player sinks into the soulsand.

Actual outcome:
The player does not sink into the soulsand.

Note that the soulsand still slows down movement.