I can see your point. They think that there is enough personality in Google as a thing. That certainly makes the most sense of what I've seen.

However I think they missed on how personal a thing it is to talk to someone. I think they should have viewed 'OK Google' as a personality that's like Google's little brother, that will ask Google for you if that's what you need or else will for example check in your diary for you.

Google doesn't need a personality. Seeing it as technology works perfectly especially when it goes wrong. It's easy to say something like, "Alexa is stupid, she can't understand a simple command", but referring to Google as tech, it is much easier to move on to reforming the command. It is also less invasive for me, personally. I'd rather refer to AI in personal terms.