It doesn't say who's 3rd choice, but considering Wildsmith has only played once for England U20s, with Walton having played 4 times for the U19s and 8 for the U20s, it's pretty clear who's further up in the pecking order.
I'm not sure it's that clear cut. Wildsmith had hardly played for Wednesday U21s this time last year but is making huge strides and is now undisputed deputy to Westwood. He's also kept 3 consecutive clean sheets in his last 3 first team games (including Newcastle & Arsenal)