The bug
Husks are exactly 2.01875 blocks tall in bedrock edition, instead of the correct 1.95 blocks. Babies are 1.009375 blocks tall instead of 0.975. As a result, they barely can't fit under a two-tall/one-tall doorway, respectively.
How to reproduce
1. Build this kinda thing
[media]
2. Stand where the armor stand is
3. Spawn some husks
→ ❌ They can't get you
It’s hard to say 1.95 is “correct” when most all full-height mobs in Bedrock Edition are actually 1.9. The husk.json entity file gives husks a 1.9 x .6 collision box just like all other zombie variants and humanoid mobs.
That being said, the actual husk heights are determined by multiplying that 1.9 by scale factors, also in husk.json. For adults:
"minecraft:scale": {
"value": 1.0625
}
For babies:
"minecraft:scale": {
"value": 0.53125
}
For other zombie variants, the baby scale is .5 and there is no scaling of the adult.
Prior to 1.13 husks had a base height of 1.8 along with other zombie variants, and the scale factor made the husk final height 1.9125 (baby: 0.95625). My guess is that these scales for the husk were implemented as the fix for MCPE-15279. Be that as it may, collision boxes were changed for several mobs to fix MCPE-45935 in 1.13. It seems that at the same time an across-the-board change to give all humanoid mobs a height of 1.9 was done for the sake of uniformity, because while zombies, witches, and villagers had their heights increased from 1.8 to 1.9, skeletons had their height decreased from 1.95 to 1.9. With this change the husk scale factors apparently were overlooked.
I've attached a behavior pack that matches the husk collision to other humanoid mobs, based on the assumption that that was the intent of the changes in 1.13:
[media]