Isn't eligibility passed means all documents necessary to make decision are there/enough?
Eligibility has to do with the criteria of the stream and CRS score you applied for: they check for the language tests, your diplomas, your work experience etc...
So this can be passed.
Then in the background check they going to look at other things like addresses, police certificates, etc...
It is not uncommon to have an ADR for a police certificate (that was not on the required list but IRCC can ask whatever they want), a divorce certificate, things like that. And these are not really part of the eligibility but part of the background check.
So if your eligibility is passed in theory they should not ask any more documents about that part (ie work experience and such) but still can ask other documents related to background check. I think there is at least one person on this thread that had eligibility completed on tracker and they still asked more documents about the work experience (but that is quite rare)