On the same topic, who determines the '10 minute' and '8 minute' time scale perfect for engagement and how did they end up with these numbers?
The 10 minutes one seems pretty arbitrary, but to arrive at 8 mins I suspect that Google studies how much time there needs to be so that mid-roll ads don't negatively affect engagement.
(Shout-out to all the wonderful, brilliant engineers working on figuring out how to minimize the user's reaction to cramming AS MANY ADS as possible down their brain)