Whoever the player is, if they encounter a strong defense then they will struggle, not just Haaland. Looking at last season, when the club faced Mamchester City, their defense received special instructions to guard Haaland, and it worked a lot. But Guardiola's clever use of other players to be the second target after Haaland and proven when he struggles to find space because of tight guarding other players who create goals. Now here we can see good teamwork.
Guardiola has a lot of attacking players in the team and many of them have leadership qualities that allow them to take responsibility and therefore it is not so easy to restrain each of these players. Silva, De Bruyne, Gundogan (no longer in the team) could create the chance themselves and score a goal, the value of such players is very high and this allows City to have an advantage. Haaland is a very talented striker, Guardiola could see that in him.