You think an EPL scouting team wasn't aware of his height before they signed him?
He's not trying to head the ball, and you don't need to be super tall to have hands that reach higher than a tall player's head.
I'm still not sure why fans are fine with midfielders that make a couple of stray passes or strikers that miss a good chance or two, but expect a keeper to be 100% error free in every game.
You only have to go back to Thursday to see a keeper with a top team make a howler from Longelo's shot. Take a look at Match of the Day on any given week and you'll see a couple of mistakes from the first team starter goalies.