YSK: Cats don't like their whiskers touching their food bowl. This is why they beg even if food is still left at the bottom.
Whisker fatigue causes stress and overstimulates their senses. Using a flat bowl or plate will relieve this issue and allow your cat to eat all their food without stress.
You can also search for "whisker fatigue" bowls specifically made for cats.
No, whisker fatigue is mostly a myth. Like just put some thought into it for a moment, do cats care when their whisters touch stuff when they are lying down or sleeping? Do they care when they squeeze into a tight space or lay in a tiny box? Does your cat rub its face on anythingnand everything it gets the chance to? Then why would only thr bowl cause whisker fatigue?