> Anyone with a clue? Thanks!

Yes, the search engines helped[1]. I run a minimal system, so when I
mount cpusets, it will actually mount cgroups with a default mount
option of "noprefix". But you likely run a rootfs with cgroups already,
so it gets mounted directly without "noprefix". Then, when the logic
analyzer tries to mount again, the implied default "noprefix" is
discarded.

[1] https://cgroups.vger.kernel.narkive.com/20fAhMNN/noprefix-mount-option

So, I will update the script to mount "cgroups" instead of "cpuset" and
use the newer filenames instead. This seems to be the proper way.

Thanks for testing, Geert!