This depends on one important question: What is the relevant market? This is a fundamental question in all antitrust law cases: https://en.wikipedia.org/wiki/Relevant_market

If the relevant market is found to be "Apps on iOS", or "Flagships phones in the US", Apple is more likely to be considered having a monopoly position than if the market is "phones in the world". The courts will have to decide on what the market is before deciding if Apple has monopoly power or not.