https://bugs.winehq.org/show_bug.cgi?id=46037
--- Comment #3 from Nikolay Sivov bunglehead@gmail.com --- (In reply to Reinhold from comment #2)
If it is just taken from uname then Android's uname is Linux.
Is there any other possibility for a Windows app to find out that the underlying OS is Android? (e.g. for macOS "wine_get_host_version" provides Darwin)
That's what uname() returns for macos kernel, it's not treated differently that other systems for get_host_version(). Currently it's used for system information report during error reporting.
If you really want to detect Android specifically you could probably look for specific Android FS paths, or wine build artifacts specific to Android.