Even if City smash a few teams, their points can come from anywhere as that team tends to share the points. One week Aguero will get a brace, the next will be Sterling then Sane etc.
At least the likes of Pogba and Hazard are more likely to be consistent.
Aye and if I was wildcarding it would be a different story as you can rearrange your team and funds as you like with no cost.
However moves like the ones above have a cost, in his case three precious free transfers and a -4 points deduction (assuming he doesn't use his second wildcard very early). It isn't just about whether his new players simply outscore his old players, they have to outscore them by enough to justify that cost of approx 16-ish points. Plus there's the potential opportunity cost of not addressing other issues that may exist in his team.
Given that City have those fixtures and someone like Sterling has managed to be the third highest scoring midfielder already (despite City sharing points as you say), I'd probably have taken a more patient approach towards getting rid of those City assets and reduced that cost. Maybe just get rid of one this week (immediately saving the -4 point hit this week), play the other against Southampton and reassess that second City player before the tougher Liverpool fixture.
Plus in general I wouldn't like selling three good attacking players in attacking teams on the week they have a good fixture as there's the potential for it to immediately bite you.
His moves could obviously still work out brilliantly and I could be proven entirely wrong, I probably just play more cautiously than he does.