Earlier quoted context omitted.
Where has this changed? Google's apps are still built on top of the SDK. The only real change was the centralization of Google Play Services, but that doesn't change the level of OS access at all and 3rd-party developers can still tap in to these services.
Play Services having a custom updater and the ability to silently gain more permissions is definitely not something available to average 3rd party developers.
Play Services must be playing by the same rules as everyone else or it just wouldn't work on as many devices as it does.