This is actually worse than the full iOS route, because Apple is likely to at least listen to appeals and implement bright-line rules between "things the app do

This is actually worse than the full iOS route, because Apple is likely to at least listen to appeals and implement bright-line rules between "things the app does" and "things users do". They ultimately do want to have developer tools on the App Store and are willing to accommodate them to a point. Even the "no competing browser engine" thing has a technical explanation: Apple wants to be able to update that part of your app without you being involved. Google just doesn't care about what your app does until they start seeing click fraud, upon which they ban your app, delete your Gmail, and ghost you. They've even done this to paying GSuite customers, game studios they were working on, and their own employees' spouses. As far as I can tell, antispam is at the top of the org chart and can overrule all other layers of management. I would never trust Google with anything I can't backup or migrate to another service.