It doesn't need to, kernel panic alone does not cause acknowledged data not to be written to the drive.

UPS is not perfect though, it's better if your data integrity guarantees are valid independent of power supply. All that requires is that the drive doesn't lie.

kernel panic wouldn't take out the SSD firmware...

To quote Apples man pages:

> Specifically, if the drive loses power or the OS crashes, the application may find that only some or none of their data was written.

mac OS's fsync(2) doesn't wait for SCSI-level flush, unless F_FULLFSYNC is provided.

macOS issues an NVMe flush on kernel panics.