Thread made me curious, so I looked at the various ingredient labels when shopping for catfood.
Friskies wet stuff pretty much consistently uses turkey as the meat base for all their foods, with a significant minority being what I’ll generously call pork.
For the fishy foods we get for treats/celebratory/bribes, the only exception is the whitefish, which is whitefish and chicken, presumably because the taste is more delicate. All the other ones have the fish at least third or fourth down the line.
So even if the fishy claims were um, not fishy, unless you’re buying super high-end cat food or cans of human tunafish, there’s not much to worry about.
Although I will say that as a bribe, tuna packed in oil is about as good as you can get.