I am guessing they say it means or want it to mean:

That it does not require periodic refreshing. Compare to getting hired and being hired until you are fired vs you can have a fixed duration contract which you would have to explicitly extend otherwise it automatically ends.

Or think about an "immortal" who doesn't age but can still be killed.

I still think this is weaseling.

That they are not specifying any particularly expiry time. In that sense it's like a "permanent" job contract.