On Darwin and Windows, users get their kernel directly from the kernel developer (because the kernel and OS developer are the same). On Linux, almost all users get their kernel from the OS distribution developer (Debian, Red Hat, etc), which is distinct from the Linux kernel project.
Thus, I don't think it is correct to look at the kernel support policy only from the Linux kernel project, but also from the distribution maintainers.
https://go.dev/issue/67001#issuecomment-2075854975 has a brief summary from last year. When a distribution chooses to support a kernel beyond upstream EOL they take on a lot of extra work in backporting fixes, but projects do commonly do that. Personally, I think we need to meet users where they are and support versions if they continue to have significant usage.
Regarding
https://go.dev/issue/72866 specifically, it is not clear to me if that is an issue with every 4.19 kernel, or some change made by this vendor. I don't think we are responsible for working around every bug that vendors introduce in their kernels, particularly if usage is low.