Android isn't competing with iOS. Apple users stay Apple users, mostly, and Android users stay Android users. Android manufacturers are competing with each other, but iPhones are their own thing.
I'm an "Apple user" that switched from iPhone/iPad/Apple Watch to Android alternatives; while remaining a happy user of Macbooks.
The statement doesn't make sense because people don't keep 2 phones in their pocket, or 2 smart watches, and rarely have 2 tablets that are actively used. And people definitely move between ecosystems. Choosing one excludes the other, and they have equivalents for each product type.
Hence they are direct competitors.
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The real problem is that the mobile OS & app store market is a stable duopoly.