It's using an advantage in one area to force concessions in an unrelated area that I believe is illegal.
For example, Microsoft had an effective monopoly over PC operating systems.
That was unfortunate, but not illegal.
It was when they used that monopoly to disadvantage a rival browser maker --- Netscape -- that they broke anti-trust law.
I'm most interested in seeing what happens over Apple's decisions to force app providers to use Apple Sign-in if the offer any other 3rd party SSO.
As a developer, I may have valid security concerns regarding Apple Sign-in.
So their app store dominance seems unrelated to SSO infrastructure. And I don't fully understand how they can force me to use it if I decide to support Google or Facebook SSO in my app.
So I do wonder if that is an anti-trust violation.