Wrong. Fingers is a 2 hour window. Most of the 1 hour windows on Cat is Hungry are wrong and are actually 2 hour windows. I've caught multiple one hour fish in the 2nd hour.
Something worth pointing out is that the game determines what will bite on your line at the moment you cast your line, which is what can result in things like casting the line at 5:59pm, getting a bite from Fingers at 6:10pm, and sites like that potentially recording the data for the 6pm window rather than the 5pm one (although, admittedly, I don't know for sure how such sites get their data).