32768 is specified as the maximum allowed area size for the fill command, but is not allowed

What I expected to happen

I would be allowed to fill an area of 32768 blocks, as it specifies that I should be.

What actually happened

I was not allowed to fill an area of 32768 blocks, even though it specified that I should be.

How to reproduce

1. Enable cheats.
2. Type /fill ~-15 ~-15 ~-15 ~16 ~16 ~16 minecraft:air into chat