Thanks for sharing. It's helpful.
But who said they can't? RTCs in the wild have been found with all kinds of critters in their tummies, not only fish and crustaceans but also reptiles, amphibians, birds, and mammals. Their mouth and stomach lining is tough and made to handle the spiniest meals. They break off pectoral and dorsal spines too should they need to.
Surely a spiny pleco is unpleasant to swallow versus say a smooth dorado but it doesn't mean it doesn't happen.