It was probably used as a generic referance, because the general public usually do not have a good mental image of what a 'Stingray' even looks like. .
You'd be surprised, most would think of a manta-ray before stingray.. Alot of people who aren't into fishkeeping are surprised to hear when I keep Stingrays, as they didn't even know FW ones exist nor were viable in captivity.. They only think seaworld.