They've mostly been trying to keep the players within their age group. Nelson's the only one that's moved up, primarily because he's been playing first team minutes for Hoffenheim, same with Sancho - otherwise they'd be with their age groups.You would think Smith-Rowe should be playing for under 20 or 21, that’s his level.
Smith-Rowe specifically has a few bodies in his way, namely one Phil Foden - who looked excellent tonight, far better than his more experienced midfield partners Tom Davies and Lewis Cook. I don't think this is a problem for Smith-Rowe - a few more games like he had in the EL and he'll get capped higher up soon enough.