That's just silly, simplistic fan talk. If you are Pep you have to juggle a set of issues at any one time. First of all you have to win games and win trophies. Then you've got to ease players back from injury. Or get them to play their way into form. You've got players who might have been knocking on your door in the summer asking for reassurances of more game time. You've got players in the last year of their contract. You've got to think about players who will be needed several game sin advance due to other injuries. And of course you've got to develop and please kids.
Pep has managed this impossible balance perfectly. Sticking Phil in yesterday would have been the highlight of his career. Of course he would want more game time but it is nowhere near as simple as that.
It's not at all. Tell me what the consequences would have been of playing Foden in some league games since January? We might be....second instead of our current position of...second.
You haven't got a clue if Pep has managed this perfectly, and nor do I, but I do know that the logic you're trying to use is fatally flawed, because obviously if you hold someone back for ages past the point you should, they'll be ready when they finally get a game.