I've always heard flats mentioned with depth....never just "flats". It's kinda like saying we caught them on "jigs". Doesn't specify color or presentation or size or anything else. But when I'm walleye fishing especially, they'll talk about 10 flats or 28'-32' flats (meaning somewhere around the 30' range) etc. Mostly to differentiate from "points" or "channels" or whatever. Or "pockets".

Pockets is even more ambiguous. Could be "pockets of fish" we had to chase. Or I've used it for any little "indentation feature" on a bank line. Too small to be a "cut" or "cove".

But that's just me...