In the IBM antitrust case, IBM was forced to separate their OS and App businesses. Their OS business had to publish all of their APIs and was not allowed to communicate non-publicly with their App business. This was to prevent IBM from using their OS monopoly to gain an App monopoly.
Once you are a monopoly, you can expect such restrictions.
What Google is really good at is evading FTC regulation by staying within FCC jurisdiction. The FCC has historically been hand in hand with industry. The FTC has real teeth.
I'm talking about the US where google is also protected by the first amendment and not the bizarro world logic the EU uses to justify their protectionism (how are shopping ads different than any other search ads?!).
"The Sherman Act broadly prohibits (1) anticompetitive agreements and (2) unilateral conduct that monopolizes or attempts to monopolize the relevant market."
For example, squashing competition by deleting your competitors search results might be interpreted as an attempt to monopolize the market.
In the context of providing a marketplace (i.e. the App Store), we aren't really looking at "private free speech" any more and so the first amendment does not apply here.
Once you are a monopoly, you can expect such restrictions.
What Google is really good at is evading FTC regulation by staying within FCC jurisdiction. The FCC has historically been hand in hand with industry. The FTC has real teeth.