He looks like a CM playing FB with a CMs level of pace. Nice technique and football IQ but I'd like a bit more athleticism from a full-back
That's way too generous on his technique and football IQ from what I've seen.
There's a long history of fullbacks and centre mids playing interchangeably because the role of fullback essentially morphed out of the "half-back" position from the W-M. The clearest traces of that can be seen in the way Guardiola plays now, where his fullbacks literally take on the role of centre mids (or "half-backs") for large chunks of the game.
The likes of Junior, Breitner, Briegel, Krol, Facchetti are among the best fullbacks in history and they all played significant periods in both fullback and midfield or as a "libero" which doesn't have a direct translation to today's game, but is closer to someone like Busquets than Pique. Fast forward to this generation and you have Marcelo having his breakthrough season as a midfielder for Madrid before going onto be arguably the best attacking left back of his generation, Roberto Carlos stepping into midfield as he came towards the end of his career, Alexander Arnold coming through the youth teams as a centre mid and potentially still going back there.
They tend to be the most interchangeable players in emergencies too e.g. Gerrard playing many early games as a fullback, Essien playing there in the CL final and many games prior to that, Hargreaves doing the same for us that season, Rafael and Fabio playing in midfield for us when we were really bare bones. If you have great running power and solid technique you can excel in both of them.
Marcelo was actually a great centre mid in that one season because his technique and football IQ was really impressive, and he got around the pitch well. Set in that context Telles looks pretty mediocre on all counts. His technique isn't bad for a fullback but CMs are generally much more technically accomplished. The Brazilian twins were pretty bad centre mids but their technique was notably better than Telles' IMO.