• we're tracking the linux kernel stable tree, not torvalds' tree which doesn't contain all tags
• gregkh/linux.git is a mirror which is manual synced, so it sometimes get delayed (https://github.com/endoflife-date/endoflife.date/pull/2386#discussion_r1088113678).
• We track it on GitHub because we can do a partial clone, which isn't supported by kernel.org

The GitHub mirror is semi-official, as greg is the kernel maintainer for the stable tree. The announcement for the mirror can be found here, and here