As I mentioned I'm not following this case really at all, but some initial thoughts from your comment are that while Apple doesn't have a monopoly on smart phones, they do have a monopoly on what software users can run on the phones and tablets they make (so if you define platform as "smartphones" then no monopoly, if platform is "iOS" then yes monopoly).
On the Android side of things, Google doesn't have near the same level of control, so that is false equivalence. One can easily side load apps, and people do all the time (Fortnite for example, couldn't happen on iOS but did on Android). There's also competing app stores (F-Droid, Amazon App store), so a very different situation. You can also run any OS you want on your device if Google's Android flavor isn't to your liking. Google also doesn't make/sell most of the hardware.
Microsoft got in trouble for simply making it very easy for people to use IE instead of Netscape and Word instead of WordPerfect. Imagine if they had gone a step further and mandated that only apps that pass a Microsoft review process could even be installed at all?