Configuration Slicer page -> "Tied Label Slicer".

I move some of my jenkins jobs to a new row and set "master" value on the left.
I expect these jobs to get this "restricted to run on master" setting.

actual:
when I open individual configuration screen for those jobs, they still have "restrict where it can be run" checkbox selected,
but the label value is empty. there is NO "master" text in it.
if I go back to Configuration Slicer page -> Tied Label Slicer, I can see those jobs in a separate row with "master" value on the left, which is good.
but it is simply not shown on individual Job Config pages (when you click "Configure" for a particular job in Jenkins UI).

note: setting labels other than "master" seems to work fine in my environment.

also, I have 0 executors available on the "master", which may or may not be relevant to this. I think it's not, but decided to share just in case.

maybe "master" is considered to be a "default" label and not always shown in some UI pages... but that's weird because I can open "Configure Job" page and type "master" value as the node restriction and it stays there...