As to what is and what isn't a tablet ... I have a SurfacePro 3 and sometimes I'm working like crazy on it from the minute I sit down until at the gate. When FA questions me about it, I say less than 2 pounds and keyboard detaches (with demo), and they respond "Is so hard to tell these days." Then I say, tablet can't stand open on their own, either needs a case that props them open or a kickstand on the back of the tablet. Usually elicits "Good to know" kind of response.
Every once in a while they persist, and I just close and tuck away.
My favorite line ever from a FA "Per the FAA, if it is bigger than an iPAD it has to be off and away." I told her the FAA would never write a regulation naming a particular product to compare to.