Video demonstration of this bug:
https://drive.google.com/file/d/1g2kxajFTBCD2AFpRY3ficatdeJsr6n2q/view?usp=sharing

How to reproduce bug:
Place down (any) slabs, cakes, (any) trapdoors, (any) mob head and heavy cores.
Make sure to put something that affects movement, such as Honey Blocks, Soul Sand or even Ice blocks.
Walk on them

Expected result:
walking on the blocks mentioned above would act like walking on a full block

Observed result:
movement acts like there's no block between the player and the block that changes movement