I don't think you are contradicting the original point.

Nobody is saying that the android team sat around in a smoke filled room plotting about how it could be all about ads. Once Android was at Google, obviously most people would be focused on making a successful platform first and foremost.

Nevertheless, the reason for Google as a whole to own such a platform is to protect its revenues streams.

Google's revenue streams rely on access to data about user behavior.

Android's strategic purpose was to ensure that Google controlled the platform so that the separate goal of capturing user information would not be threatened by other corporations.