I'm pretty in the dark here since I don't have a google account, but what are these private APIs they're talking about? Is Google Sync the equivalent of Firefox

I'm pretty in the dark here since I don't have a google account, but what are these private APIs they're talking about? Is Google Sync the equivalent of Firefox Sync? If that doesn't work, but the actual browsing works, what's the big deal? People should still be able to build Chromium and their Electron apps. It's not clear to me what people are getting worked up about... what am I missing?