For the duration of a major release, up until ~x.4 pretty much everything from upstream gets backported with a delay of 6-12 months, depending on how conservative to change the rhel engineer maintaining this part of the kernel is.

After ~x.4 things slow down and only "important" fixes get backported but no new features.

After ~x.7 or so different processes and approvals come into play and virtually nothing except high severity bugs or something that "important customer" needs will be backported.

Sure, they aren't backporting patches wholesale. But the patches that did get backported, if any, needs much more scrutiny given the situation.

The thing about enterprise Linux distros is that they have a long support period. Bug fixes and security patches pile up.

Fortunately though, xz doesn't seem to have a lot of backported patches.

https://git.centos.org/rpms/xz/blob/c8s/f/SPECS/xz.spec https://git.centos.org/rpms/xz/blob/c7/f/SPECS/xz.spec

But take glibc for example. The amount of patches makes my head spin.

https://git.centos.org/rpms/glibc/blob/c8s/f/SPECS/glibc.spe...