It is up to date, with security patches and fixes. That is obviously what is relevant here. That is why the parent comment got down voted, since it is up to date in context of a security vulnerability.
It should be even more secure, since new software versions might introduce unknown attack vectors.
I am saying that any version of Ubuntu is not representative of the mainline kernel, which is what is relevant when it comes to analyzing current mitigations.
Distro LTS releases often mean custom kernels, backports, hardware enablement, whatnot, which makes it effectively a fork.
Unless were interested in discovering kernel variation discrepancies, its more interesting to analyze mainline.
I'd expect an awful lot of production workloads to be running on LTS kernel versions (and likely also LTS distro releases). So the mitigations currently available in an LTS release of a mainstream distro are quite relevant.
They are running their LTS distro's LTS kernel, but that us not an upstream thing
On an LTS, you'll be running a Canonical kernel, or a Red Hat kernel, or a SuSE kernel, or an Oracle kernel, or...
Each will have different backports, different hardware enablement, different random patches of choice, and so different bugs and problems.
Unless were evaluating the security of a particular distro release, mainline is what is Linux and will ultimately be the shared base for future releases.
Edit: "LTS" added due to popular demand