Yes, but in that specific example you could also simply use a signature, as the fact that you are part of a single org reveals all information.

If you were part of multiple orgs and just want to prove you're part of any of them without revealing which in particular, then a ZKP can help.

Yea you can prove you're some set of users without revealing which one.

This is useful in the case of whistle blowing you can prove you do work at a company, or say a US Senator can show the government is up to no good and prove they are a senator without revealing who they are.