What “philosophy” exactly? He’s managed to win the league every year, each time with fewest goals conceded, so I think if he has a “philosophy”, it seems to work quite well.
Right now he’s lost three games, which can happen, but his team has also certainly shipped too many goals for his liking. His best defender and captain, however, has played all but 116 minutes this season. I doubt our defensive record would be much better, if Kos was out that long. The talented young centre back they bought in the summer, who surely is supposed to play alongside Kompany and learn his trait some more, is now relied upon all the time and is highly error-prone. New system, new club, new manager. His performances are to be expected.
Given the circumstances, an on par start to the season for Guardiola and City, nothing more, nothing less.