On macOS without a full Xcode installation, flutter doctor says:

[✗] Xcode - develop for iOS and macOS
    ✗ Xcode installation is incomplete; a full installation is necessary for iOS development.

This is confusing: the first line says Xcode is for iOS and macOS, but the second line only mentions it's necessary for iOS development. However, the fact is Xcode is necessary for macOS development, too.