But there are many other distribution channels for mobile apps, the Google Play Store, F-Droid, etc. Surely "iOS devices" isn't a "market" in and of itself, and the markets are "mobile apps" and "mobile phones".
Same reason "McDonalds hamburgers" aren't a market. They're just a branded product within a larger "smartphones" market.
> How do you define market, then, if that's not a market?
Same way the FTC does:
> all goods or services that buyers view as close substitutes
https://www.ftc.gov/advice-guidance/competition-guidance/gui...
An Android is a close substitute for an iPhone, just like a Ford is a close substitute for a Toyota. People switch between them all the time.