It seems obvious, but I think an important part of science is to remain skeptical and not accept things as fact because they’re “obvious.”
It very well could have turned out that the mice still chose to eat despite having no hunger. I for one am definitely prone to overeating past the point of satiating hunger, or eating even if I’m not hungry. I find it satisfying and a way to overcome boredom; or maybe a better example is my dog, who I’m pretty certain would eat himself to death if I left his kibble box unlocked.
It seems obvious that the sun revolves around the Earth, but we now know that isn’t true. :-)