Everyone so quick to deny this.. I think it's dependent on whether or not XP is given with the extra cooked fish. There are other similar functions in game, one main example being the ability to smelt an extra bar from a singular set of ores. Super donators have perks like gaining extra noted supplies from fishing, woodcutting, mining.. this doesn't seem much different to me.
I could see why this would be a suggestion to hear out. And while I don't necessarily think it needs to be added, I think there should be more discussion about the idea, and ways it could work better.