I understand what you are saying but in nature they typically are not found in the tidal regions near the shore but more in the 30+ foot deep range. If you Google linckia sea stars
you will notice that 99% of all the images are shown with the linckia sea star underwater. Where as if you just Google Sea Star
you can find tons of photos of red, sand, ect type sea stars on rocks out of the water in their natural environment.
Finding documentation for well respected authors is difficult. Found this on www.wetwebmedia.com
by Bob Fenner:
"Echinoderms are aerobic organisms; although some may stand extended periods of low levels of oxygen or exposure to the air, others do not."
there is this:
"Sea stars typically are found on sandy of mud bottoms, though Linckia guildingii, an occasional Caribbean species, is found on reefs from 7 to 40 m of water."
That's about it and I agree that the "air exposure" argument is a bit misleading and more then likely deaths should be attributive to short acclimation and osmotic shock more.
I do take Live Aquaria's advice to heart more then most "fish dealers" though as most of their info is dead on in other areas.