When on a fence, you float one block above them instead of actually walking on them. This affects all mobs if they stand on a fence.
Comments 3
Thank you for your report!
However, this issue is Working as Intended.
The behavior you have reported is working as intended. Fences have a 1-1/2 block high collision box to prevent mobs from jumping on top of them. A block's collision box determines how close any mob or player can get to it.
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Works as intended, this has always been a thing.
The fence hitbox is of one block and a half just to make mobs unable to jump through it.