[adventured]

Market share doesn't determine anti-trust action, it's merely one factor that tends to play a role in the ability of a company to harm consumers.

I don't know why this myth about % market share and anti-trust refuses to die.

Harm to consumers is the primary consideration. Apple has that ability through locking up component supply in an aggressively exclusionary manner that restricts competition, which then harms consumers. If Apple perpetually uses their very elevated profit margins to lock up that supply, you can bet they're plainly raising the average cost of a smartphone by limiting how many other lower cost competing devices there are eg at TSMC 3nm.