Yeah I struggle with these takes tbh.
It feels like old thinking, like well he is a midfielder and is playing well at LB so he will be a future midfielder.
Like that logic doesn't really hold, but yes I can definitely see him play in midfield for sure.
But the modern game for the top teams both tactically and physically is all about how the coaches are using their fullbacks (Pep, Flick, Arteta, Kompany , Maresca)
This is where some games are being decided, how well you can use your fullbacks to frustrate the opposition by getting an extra man.
If O Reilly is as good as we all think, then LB is literally perfectly for him and Pep for tactical flexibility.