The Raphael has the nickname "Caiman-Killer" because when a Caiman tries to swallow them, they brace out their spines and choke thee Caiman to death and you think a predator less than 1/16 the size of a Caiman will have better luck eating them?
I too find this surprising but there is plenty of what I don't know. Any supporting information, links, etc.?
Many catfish lock their pectoral and dorsal spines in response to an attack - bullheads, synodontis, Doradidae, wood catfish, walking catfish, etc. but they are still eaten by many predators of water, land, and air. I think the fish predators just need to be large enough and have the instinct on how to deal with spiny prey like that.
Bullheads are one of the favorite meals for flathead catfish. IDK how they deal with the spines but they eat a lot of them even without too great of a body size disparity, it appears. Maybe they break off the spines.
necrocanis
reported that his flathead fought with its tank mate catfish and broke off their spines easily. All the cats were under a foot or so.