Anti-trust is about anti-competitive practices and consumer benefit. Carterfone and Microsoft are possibly the most relevant examples. Google and Apple are a duopoly in the phone market, and Apple's (and Google's in the case of Epic) behaviour towards these companies could be seen as anti-competitive.

If you want to run a platform business, you'll need to be mindful of anti-trust law more than anything else. The Apple platform is perfectly capable of anti-competitive behaviour given it's market share, and doubly so given Apple and Google control 99% of the phone market.