This is true, but Google may have more leverage than they think. If the phone vendors don't like the direction of Android what are they going to do, switch to Windows/Tizen/webOS/FirefoxOS?

Only it the technology pretends that business/greed somehow does not apply. Google could make selling updates on the Play store an optional part of treble, problem fixed.

You are wrong. Sometimes it is possible, sometimes it is not.