ACCORDING TO MIRIAM WEBSTER DICTIONARY IT IS

“The word hot dog refers either to the sausage that you buy squeezed in a plastic package with 7 or so of its kind, or to the same sausage heated and served in a long split roll. When it's served in the roll, it's also a sandwich. We know: the idea that a hot dog is a sandwich is heresy to some of you. But given that the definition of sandwich is "two or more slices of bread or a split roll having a filling in between," there is no sensible way around it. If you want a meatball sandwich on a split roll to be a kind of sandwich, then you have to accept that a hot dog is also a kind of sandwich.”

IF SUBWAY SANDWICHES ARE SANDWICHES THEN HOTDOGS R SANDWICHES