Didn't Ball come out and say he loves it in CHA and is not looking for a trade?
In any case, I don't think it matters whether he fits your definition of a PG or not. In my mind, he is a PG in the same way that Gilgeous-Alexander is a PG, Or Haliburton. Or even Derrick White. Any of them would have difficulty defending small quick guards. And now many traditional PGs are there these days. Most teams' primary ball handlers are combo guards. And that is what I see Ball as.
Being called a combo guard used to be a negative thing, but I don't think it is these days.