Unfortunately the adhesive manufacturers have been stretching the meaning of "thinset" and "mortar" for many years. I don't know who was the first abuser, but I guess once one did it the rest thought they also had to.
Thinset Mortar & Mortar by definition must be made from Portland Cement. Portland Cement can not be stored once mixed, it hardens in a matter of hours. Pre-mixed products do not contain Portland, and so can not be thinset mortar. But who's gonna tell them they have to tell the truth?
That product and those made by all the other manufacturers are really mastic with a little sand or ? mixed in the give it some texture. They are fine for vertical dry areas such as backsplashes, not a good product for wet areas and makes no sense to use them on floors.
Jaz