Powder snow will only slow down the player if the bottom of their hitbox is inside of it

Can confirm in 21w07a.

Can confirm in 21w08b.

Video attached.

Can confirm in 21w10a.

Can confirm in 21w11a.

Can confirm in 21w13a.

Can confirm in 21w14a.

Can confirm in 21w15a.

Can confirm in 21w16a.

Can confirm in 21w17a.

Can confirm in 1.17.

I can confirm this, and it has broken my mob grinder, which works on a basis of freezing.

Can confirm in 1.17.1.

Can confirm this behavior in 21w42a. Here are some extra details regarding this problem.

The Bug:

Powder snow doesn't slow down entities if their feet aren't directly inside of it.

Steps to Reproduce:

• Build the setup as shown in the attachment below.

• Walk inside of the powder snow and as you do this, pay close attention to your movement speed.

• Take note as to whether or not powder snow slows down entities if their feet aren't directly inside of it.

Observed Behavior:

Powder snow doesn't slow down entities if their feet aren't directly inside of it.

Expected Behavior:

Powder snow would slow down entities even if their feet aren't directly inside of it.

Can confirm in 1.18.

Can confirm in 1.18.1.

I can confirm this in 22w07a. Here's a code analysis regarding this issue.

Code Analysis:

The following is based on a decompiled version of Minecraft 1.18.1 using MCP-Reborn.

net.minecraft.world.level.block.PowderSnowBlock.java

public class PowderSnowBlock extends Block implements BucketPickup {
   ...
   public void entityInside(BlockState $bs, Level $l, BlockPos $bp, Entity $e) {
      if (!($e instanceof LivingEntity) || $e.getFeetBlockState().is(this)) {
         $e.makeStuckInBlock($bs, new Vec3((double)0.9F, 1.5D, (double)0.9F));
         ...

If we look at the above class, we can see that two checks are carried out before the game considers an entity to be stuck in powder snow. If we focus our attention toward the second check within the "if" statement above, we can see that the entity's feet must be inside of powder snow in order for the makeStuckInBlock() method to be called, (for the game to consider the entity stuck in powder snow). This is evident through the following piece of code:

if ... || $e.getFeetBlockState().is(this))

Because of this, only the freezing effect and not the block's movement reduction slows down the entity when their feet aren't inside of powder snow but other body parts are.