I opened a post a year ago and waited for a reply, but Gmail messed up, so it only sent me a recent update of it 5 hours ago, not before when I was questioned for more info, and is now closed.

It's https://bugs.mojang.com/browse/MCPE-15626 (MCPE-15626)

Although I think now hunger is not affected by difficulty intentionally.
If you want me to put it here, this is the bug:
Mob spawn rates don't change in variation of difficulty.