Hopper hitbox is too large

In terms of Java/Bedrock edition parity, note that this issue was fixed long ago for the Java platform. Also note that in Bedrock we can click items visible through gaps in stairs and slabs and even between chests, so it’s inconsistent behavior within the Bedrock codebase to not be able to reach items that are visible behind a hopper’s funnel.

Original version of this post includes quite a few comments, including some from @mega_spud, that demonstrate additional issues with the hopper hitbox. See: https://bugs.mojang.com/browse/MCPE-13758