That picture seems to show they've got about 80 units in stock..
They won't know much about the units, they are just resellers.
That warning came from Airtap's marketing or legal dept, years ago.
It's likely because they didn't know if the refrigerant coil inside the tank,
could take 212F, if the over-heat protection on the heating elements failed.
(Leaving 230vac on continuously).
I used DC at about 100V@8A and wrecked my new GE tank's controls. They are toast.
If I hooked up 230VAC now, it would never shut off..