The problem is that disks are confirming writes before they actually store the write in the non volatile target.
Consumer NVMe's are bad about this. They'll fill a write buffer on the drive and flush it when it is convenient for the device, regardless of what the OS wants.
The Samsung 963 NVMe is an interesting device though because it has little capacitors on it that will flush the contents of that buffer when power is suddenly lost. But it still also just fills that write buffer and does not commit to disk when it said it did.
This is how they are gaming the benchmark tests.
As long as it's truly "past the point of no return" I don't particularly care where the data is stored (QLC, SLC, DDR+Capacitor). I just care that the confirmation happens after the data in no longer able to be lost. I'm okay with the first 512MB getting confirmation very quickly because it's going to volatile DDR RAM on the SSD package -- I just want the hardware to guarantee that there's enough stored energy to eventually write any confirmed data. This doesn't need to have a huge impact on performance.
This goes for either a power loss event, or kernel panic. Either way, the hard disk should eventually store all confirmed data in a non-volatile way -- even if it's not yet stored non-volatile at the time of confirmation.