the only anticompetitive element I can think of is the way they pushed their scanning app to Android phones with Play Services. On IOS they're not in control but still able to launch an app (app snippets the feature is called, I think?) but on Android they themselves killed off Instant Apps because nobody used it. If one of Google's competitors like hCAPTCHA tries to do the same, they'll have more friction on Android than Google does.

When it comes to GrapheneOS, it's the website owners that decided to block those devices by using this service. There are other services that don't block those phones they can use instead.

That's the whole goal of the concept. Safetynet (the predecessor of Play Integrity) was developed to block CyanogenMod and then later used to block Huawei.