I'm pretty fine with the script kiddie thesis. But if we go for an intelligence agency, we have to explain why the hack was so.. small. A local privilege escalation that is relatively easy to find* should be of very limited use at best. They(tm) get ability to fake linux kernel source and that's all they do!?

* Even if the linux kernel folks had failed to notice the CVS hack, someone would have eventually diffed the kernel versions and found it. Assigning uid to 0 is rather obvious, and quite a lot of linters warn about assignment in comparison.

But if they had included (for example) some sort of off-by-one buffer overflow, the hack would have been a lot less apparent. Now do that for a remote exploit, and they get way more possibilities.