In a way it doesn’t matter if the OS can recover because people don’t think it will, and it also says “do not turn off your computer”. It’s not at all hard to imagine people feeling glued to their desks or afraid to take the machine away with that information.

If the OS can recover, it should just say “you may still shut down at any time but the update will start from the beginning if you do”.

Yup, done so as well. I was surprised it went well!