You’re running last years race, and forgetting not only what Pep said about Walker, but the fact that Walker was dropped multiple times at the end of last season.
What is NEXT SEASON’S iteration of Pep’s City is what we are talking about.
As for his “licence to roam,” I think you are confusing the fact that Pep was using him as a midfield overload last season and it wasn’t until the second half of the CL that Pep told him to push forward, into the 8 position (to get behind the Inter press or drag them back) that Stones truly “roamed” at all.
Previously, Stones role was as a second player to overload the opposition midfield when they pushed a midfielder up on Rodri or pulled their CF back to mark him.
City need to create the angle for the DM to pick up the ball if he is going to play the pivot role. If Rodri is being man-marked, we had been shifting it wide to Akanji/Ake/Walker, but teams realize these are the weakest ball players in the team, and are constrained by the touchline, so they can squeeze them and force the long ball or a bad/hurried pass into an already tight midfield.
What the SECOND DM does is to create another angle for that “behind the first press” pass to release us into midfield.
If you watch, Rodri & Stones are involved in a simple “dance” where they keep sliding left/right or forwards/backwards to be available for the pass. Their movement is not choreographed but decided by the movement of the other players and whether the other DM receives the ball or not. It’s simply triangles in fluid motion to create the angle for that first attacking pass, so that the ball can then be played wide or through to the striker(s).
Against a retreating opposition, there is no need for a rigid Back 3, or especially 4, so we often find ourselves with only two “defenders,” even though they are ball playing defenders, often well inside the opposition half!!!