But Android is still Google's OS, so they have the right to put it on whatever device they want, and they can update it whenever they want.
You don't understand the concept of "open source" at ALL, do you?
Yes, they can put it on whatever device they want. Yes, they can update it whenever they want. Neither of those two conditions have a single thing to do with anything regarding when manufacturers or carriers push out updated versions of the OS to devices.
Nothing.