I have read the first comment in your link and just replied to it. Pretty sure it's incorrect as I've seen a LineageOS device in September with a September security update level, and you can see in Gerrit[0] that the version string bumps are merged every month, with the commit messages including which CVEs were fixed. New images are built weekly[1].

What I think happened is that GrapheneOS assumed the blog post meant that those updates happened at the time of the post, while the post is actually announcing things that were done in the last few months.

[0] https://review.lineageos.org/q/subject:%22release:+Bump+Secu...

[1] https://download.lineageos.org/devices/frankel/builds