I have not been able to confirm if this was the case at the time of implementation, but when you changed the specs so that the hopper could suck items that were more than 1/2 block and less than 1 block, the hopper could suck items even if the hitbox was 1 block high at a mud block.
Also, Soul Sands has a hitbox that is 1 block high, but the hopper can still suck items!
Observed Result
The hopper sucks in items on a block that is 1 block high in the hitbox.
Expected Result
Perhaps the hitbox display should be changed to show less than 1 block.
Or maybe Mud Blocks and Soul Sands could have been made as blocks where items could not be sucked into the hopper.
Thank you for your report!
However, this issue is Working as Intended.
The report you have submitted is working as intended, based on MCPE-55824 having been fixed.
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Things such as graphics, sounds, world creation, biomes, redstone, villagers, and animals may not work the same in current versions.
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