Not always but in a lot of instances, when cats do that "but I can see the bottom!" thing, it's because the bowl may be too small and their whiskers hit the sides and they don't like it. Some cats are just assholes though lol

What happens to “Bella you asshole cat you don’t count”?

My two are rescues also, and they are very good about food. They eat from the bowl, but they don't overeat. I expected cats that had been so dangerously undernourished as kittens would have overeating disorders, but they are very good.