1) Yes, mostly. The XD is cheaper, though not entirely comparable.
2) Several GPD models have gaming controls as well as the keyboard, and at least one has just gaming controls.
3) Doesn't surprise me.
So yes, with all the above considered, I'm not surprised Steam is seeing if their version will do any better. It wasn't a criticism or an opposition. I hope they do well.
That said, I mostly play M&KB, so having only gaming controls isn't a selling point for me.