My new computer takes a while to POST (z690 with ddr5 smh) so it’s basically been continuously either on or in sleep since I built it 18 months ago and I’ve had an unexpected shutdown due to power loss once in that time according to the Event log. I think the risk of losing power while flashing the bios is very small in real life unless you are stuck in a place with third world electricity infrastructure.
If POST takes a long time it’s often memory training, backing off on the timings just slightly might make it go a lot quicker. Bios updates also often twiddle knobs in this area.
Memory training can happen if the CPU detects that current timings don't work at boot. Since GP never shuts down, it's possible that his memory is always hot and performs better on a reboot (when setting new timings) than after a cold boot (this is basically always true since ram chips like to be hot but especially relevant here). If GP is using XMP or has custom timings, I'd suggest easing off on them especially considering the novelty of DDR5.
It isn’t this, it takes about a minute to train after a bios update or when I enable XMP but never trains after that. It just takes like 20-30 seconds to get all the way to the bios splash screen and only 5 seconds to return from sleep so I just use sleep instead of turning it off. Then the only time I need to wait through a boot is for windows updates.