We can manage this though ...
Why doesn't boost pause during the 'personal timeout'? Well, this is something that we as players are able to manage. We can decide when to play, how long to play, and at what point during the play session to boost. Just like we are able to decide when to raid based on battery life. You wouldn't start a raid session when your device is at 5% battery and unplugged, right? I think the results would be predictable. Just like shield management, players have to manage boosts so we get the most out of our boost session.
The pause during the maintenance break is because they can happen at any time, and the dev team isn't always able to give us players a heads-up, depending on the urgency of the break. So we got a pause feature that helps out those who may be boosting when a maintenance begins.