[dontreact]

In my experience, yes. Most people find it courteous to inform their manager but I did a lot of 20% time that led to getting hired with Google Brain, and it was never any doubt in my mind that my manager would approve.

That being said, there were times when I was really excited about the project so I would work 80% time plus 40% time and stay late.

[nlpleb]

Can you tell us about what exactly you did that led you to getting hired with GB?

[dontreact]

I don't want to get too specific but I did a 20% project that led to a couple of conference abstracts with one subteam. This built relationships which helped when I applied internally to work on a different subteam.

20% time aiding in team transfer is very common I think.