Is the build date, not connected to the Android SPL which you require. I wrote this recently Eos Web Installer Support improvements - #11 by aibd.
See also (answered) Install /e/ on FP5 with newer Security Patches.
Maybe also of interest https://www.reddit.com/r/LineageOS/comments/n7yo7u/a_discussion_about_bootloader_lockingunlocking/.