I suspect that Poch rates KWP's potential but thinks he's too physically weak to be trusted right now. He barely featured at all this season after he was absolutely bullied by Antonio in the cup match against West Ham. He's still a young lad an will develop physically over time, and with 5-10 pounds worth of upper body muscle he'll stand a much better chance of matching up with Premier League wingers. That would explain why he never gets selected but also why he's been kept around.
Agree, he is too lightweight. Doesn't seem to take much to brush him aside and that won't cut it in this league. He isn't that young either now. Even though he is 22, he looks like a boy up against men at times. I'd give him this summer to really work on his strength and then have him as backup to a new RB next season and see how he gets on. Trippier and Aurier can both go for me.