That happens? since when? I have been running windows 10 since release and not once has it ever attempted to update while I was using it. At most I have a message in the action center saying updates are available and ready, or that it will need to reboot to update, but I have never had a forced update/reboot occur during usage
Theres a reason there is an 'active hours' setting. It specifically states that windows will never automatically reboot due to an update during active hours with a note below that states 'We'll check to see if your using the device before rebooting'
So............you havent been paying attention maybe?