You can access Gmail over IMAP and pull down messages locally. If you do this; Back. Up. Your. Mbox.
Also, fun fact, you can move messages from a local mbox to Gmail while preserving read status and original dates if you want to add old email to Gmail for some reason.
That’s exactly the point of power loss protection (aka PLP.) As a side effect of not needing to wait for a flush after a write synchronous write workloads are dramatically faster on enterprise drives with PLP.
Edit: To add a bit of detail - you don’t need to wait for a flush after a synchronous write with PLP because the drive firmware can lie and immediately return from a flush call because there’s enough backup power to complete that flush if the power were cut.