i'm not sure what you mean by "choice on ad surveillance", but my point was about anti-trust, not simply anti-competitiveness or monopoly. anti-trust is using market power in one segment to distort another one unfairly.
the precedent you point out is what helps apple claim they're not a trust, because the two components, ads and content, go together in one business model. with google, being paid to place ads is the business model, and competing in the various channels for those ads are potential anti-trust encroachments because they're different markets.
as is usual in these cases, the harm is an inflated market price above the non-distortionary baseline.