I'd be surprised if thats right. Phil was clean through twice in one half through superbly timed runs. Grealish is never in that position. I could be wrong as who knows what Pep thinks but I'd prefer 2 one on ones than retained possession
I think Pep likes them both for different reasons.
In 30+ degree heat, in the blazing sunshine, early in the season at a point where not everyone in the squad is 100% match fit, when you're 3-0 up against a Bournemouth side that don't look anywhere near a comeback, your priority going into the second half shouldn't be about how many one-on-ones can be created.
Your priority should be retaining the lead and managing the game with the least energy expended as is possible while tiring out the opponent to even further reduce their ability to come back. Yes, if chances occur, try to take them. But keep the ball, manoeuvre the opposition around, stay focused and professional and don't wear the team out unnecessarily.
I think at their current points in their careers, Jack's more suited to delivering that plan than Phil is. And it's not like Jack doesn't create chances, so it's hardly a defensive move that reduces creativity or represents shutting up shop.
Making that change enabled Pep to field the right personnel to fit the change of plan, give Phil a little rest given the challenging conditions and his lack of pre-season, and give Jack a boost of confidence by giving him game-time as a reward for his recent performances.
Maybe he also used it to lightly make a point to Phil about decision-making. But I'm not convinced that was the main thing in his mind, and even if it was I think it will have been much less of a deal than many are thinking.