That doesn't entirely get by the acquisition test. Google acquired the HTC smartphone design team for $1.1 billion.
See https://www.theverge.com/2018/1/30/16949366/google-htc-smart...
See https://www.theverge.com/2018/1/30/16949366/google-htc-smart...
This suggests they at least partially outsourced the work initially and then acqui-hired their way into in-housing it.
Though, yes, it is possible that some of it was done in-house from the beginning. Just because they leaned on external resources to some extent doesn't mean they developed no internal capability on their own.