They are perfectly edible at that size, I know for a fact.
Maybe a giant blue channel cat from the bottom of a Lousiana spillway is edible, but not a California lake bottom leviathan. We caught a 39 pounder out of Lake Perris CA and it was 100% mud.
Just me talking here, but farm raised catfish is about all that’s edible.
By the way, Lake Perris has catfish in there that’ll snap your pole off at the reel. It was like pulling a sliding glass door off the bottom of the lake. Was sure we were snagged until the line moved. That monster had a half dozen broken hooks embedded in its lip, some of which had completely healed over. Sounds like a BS fish tale but a cat that size is only uncommon.