It's not only during the master restart. It affects every build started before restart.
Due to some other issues I have to restart Jenkins every week (number of open files is rising to the point where Jenkins is not usable). As a result I'm observing this issue every week, and have to cancel builds started before reboot.
My observations are a little different than the issue description. For me, throttle for the running pipelines is forgotten during the reboot. All new Jobs after the reboot are throttling correctly but they are not respecting throttling that happened before reboot. This leads to builds deadlocks and is very frustrating because builds takes a really long time in my case.
I did not observed throttling problem during or after the restart but I haven't done much testing either. For me, it affects every single build started before reboot, making the Pipeline durability totally useless (meaning it can resume after master restart). I have to abort such build anyway because new builds will not see throttling of that build.