That's not what the courts have been saying lately. iOS app distribution and Android app distribution have both been called relevant markets in recent trails.
The first half of your claim is false, "iOS app distribution" was not accepted as a valid "relevant market" in the very court case being discussed. But I think you knew that already.
I think you're conflating their designation as "markets" because they are marketplaces of apps with the economic term "markets" which has a specific definition for a sector of industry.
no conflation at all. read up on some of the trials for Google and Apple over the last couple years. The anti-trust trials aren't talking about a "super market", they're talking about a relevant market in anti-trust context.
You’re discussing this in the context of a case that deemed that it wasn’t an anti-trust violation because it was determined Apple doesn’t have a monopoly, though. They’re not considered their own markets.