The phone manufacturers don't have much of a choice unless they are willing to ditch support for all the proprietary Google parts of Android. People probably won't buy android phones without play store access.
So yes, phone manufacturers have a choice here, they don't have to make Google the default.
I wouldn't recommend it for privacy, but them giving me the choice means manufacturers can do this if they want.
I agree Xiaomi loves their data collection to the point of selling pole fan that require an app to operate - I saw that one in one of their stores.
So what else is there?