Given that Google has a history of accidentally breaking things in YouTube that only impacts Firefox, I'm 100% certain they can be trusted to muck around in apps written by others.

Think of the opportunities. Next time Google releases a new social media system they can automatically add it into every existing Android app as a login option!

Google dropping their payment system again? Not a problem, they can just change everyone's billing code.

Or when they do the monthly random feature deprecation on Google cloud they can just modify any code that accessed it, across all apps!

Why bother testing when your app code could be changed at any time by Google. The time and cost savings will be massive.