I asked a similar question here: Hide client to commercial, not a full solution so far.
I am also using Eldy as default, but the behavior is different here. The users can’t see other users assigned third parties.
The workaround I used was to create a specific third-party for specific users. This way, even if the user shares something in common with the third party, they can’t see each other work.
It is madness if we have a lot of third parties. Hopefully, it is not my case.
I don’t know if this clue may help you. Sorry for not being more useful.
