"Technical decision" is all he says, and it's very unclear as to what that means.
I have a theory based on nothing that Ward is actually a good personality to have in the changing room, and that's why he's being included in the matchday squad.
It's the only thing I can think of that makes sense.
Otherwise, if you're that worried about 2 keepers getting injured in one game, you just get Choudhury some extra Keeper training sessions. (Only half joking there...)