You brought up the stats dude, not me.
If we want him for wing back first, and for the wing in a 4-3-3 option secondly, I'm not sure what you'd want from him that he hasn't shown already. He would suit our two preferable systems for the season massively, and brings both natural width and quality with it which we've been lacking. He'd be playing in a much better team which should hopefully help him to up his production.
Compare it to Navas. Navas had 6 assists in 36 games for Sevilla the season before last, but at City managed 7 in exactly half the games as well as adding 4 goals. He added a new dimension to them as they gained natural width and not forced.
At wing back, I just want someone who can work hard, has pace, can tackle well and has quality on the ball to back his pace up. He ticks all the boxes.
I agree, the money is a lot. But if Van Gaal wants a winger who can play on either side for a 4-3-3 and isn't happy with our wingback options, then it's a 'two birds, one stone' situation. It's not a compromise either since I don't think there are better players available in that position bar perhaps Di Maria.