My understanding of the story is Android was nearly completely re-written after the iPhone announcement. The first Android phone was very different from what Google purchased.
Well, android is open source so manufacturers can add their stuff and manufacturers decide when to update their devices (if at all). Google is being more strict on updates, as well as adding Project Treble which makes updating a device a breeze.
At the time... yes. That's the point of an acquisition - to buy talent/skills/tech when you don't have that talent in-house (or to augment existing talent).
Now, many years later and with normal amounts of turn over? That's a different question all together.
Given that at acquisition, the android team was <30 people, and it had to be mostly rewritten before it was originally launched, and has been significantly changed since then, I think this is blatantly false ;)