I find that in order to get the entire dorsum of my hand and wrist on the wall with this move, there is some bending of my elbows, or if I lean somewhat to the side making contact, in which case both dorsal surfaces can't make 100% contact at once (the proximal portion of the wrist tends to come up when I go to the middle or the other side).
I wonder if this is a acceptable, or if it indicates a lack of mobility I was unaware of (despite having done normal complete wrist pushups, albeit without the benefit or critique).