Keyboard backlight keeps its level through a second blank
A change merged into quattro records the keyboard backlight only when nothing is already saved, and restore consumes that record, so a second blank before wake does not save 0 over the first.
After a suspend from the lock screen, the keyboard backlight comes back at 0 on unlock. The lock can blank again before a wake, and that second blank was saving 0 over the level the first one saved.
The lock re-arms its blank without a wake in between: after a resume it sees while the displays are off, and when a screen arrives. A backlight that was off before the lock stays off. A level that cannot be read is left lit rather than blanked with no record of it.