There's a curious parallel between Android and Windows. For WinXP and earlier, OEMs made all sorts of changes, pre-installed lots of random software, and generally just broke things. Microsoft started cracking down, to the point that modern Windows actually kinda works, and OEMs have very strict limits in how they can customize it.

For early Android 2.x devices, OEMs customized everything. Now Google's cracking down. Also, by moving functionality out of AOSP and into Play Services, Google's able to ship new functionality to old devices, raising the bar and making it easier for developers to support those old devices. This sort of updating also has important security benefits (e.g., patching security bugs in the WebView component).

I suppose with the EU is going to have to grapple with is the extent to which these sorts of moves, taken by Google, were done for anticompetitive reasons or whether they were done for other reasons. And even if the motive was pure, was the downstream effect still legal? I expect there to be a lot of wrangling along those lines. Google might point to seemingly obvious examples, like all the steps they take to disadvantage SEO. Is it anticompetitive to nuke web sites that try to game your rankings? Certainly not. Is it anticompetitive to set baseline features and requirements for Android, which helps developers and protects users, if it disadvantages third-party platform developers? That's where the fun will happen.