I'm quite surprised at some of the posts above.
Remember the situation, as described, pax goes to QF lounge, asks if EK lounge is open (or if they can use it). QF staff say no, and add that they can't use it.
Pax is NOT asking about ability to access the lounge s/he is at the entry to. Further, pax is enquiring about EK lounge, so oneworld is not applicable.
The "issue" here is staff putting in their 2 cents that the pax wouldn't get access to the lounge.
Now some here have suggested it's a lie designed to push pax (and others) away from accessing EK lounges *on purpose*
I counter with... I very much doubt it.
I'd expect a lounge agent to know the rights of any particular pax arriving at the lounge they are manning. We all know, of course, there are many examples where they do not (LAX being a good example) but that issue aside, I would NOT expect an agent to know the access rules to any other partner lounge.
The fault here is in the agent thinking they know, when clearly they don't.
Deliberate? On reading the OP's post where similar advice was given in 2 different locations you might think yes, it's a conspiracy/deliberate instruction by QF. It's possible, but honestly I doubt it.
There have been times in my professional life where I've honestly beieved something to be true and said as much to customers or colleagues and later proved to be incorrect and I've felt like a goose and at times had to apologise. Now when I stated something I honestly believed to be true I never considered to go look it up to verify that (until obviously I might have had to, or someone challenged me on what I thought and shoot yeah I did verify). Maybe that's arrogance, but if I was a CSR at a busy lounge I don't know that I'd be second guessing requests like this to then go back and look.
Having said that if pax said to me "Can you please confirm this?" then as a CSR I think I would need to rather than just stick to my idea of the truth.
And in the situation where the OP asked if the Ek lounge was open they did not ask if they could access it. The CSR ventured an opinion (incorrect) but I repeat as I wrote the other day... how many people would actually come to a QF lounge and even ask if they could access another partner's lounge? I would wager a very low number. I reckon the CSR was trying to be "helpful" even if supplying incorrect information.
Let's not forget that even at some locations there are weird arrangements for lounge use - eg VA J pax at LAX use the Ek lounge, UA J pax at MEL use CX (not NZ or SQ which is weird), or QF directing poor souls to the AF lounge at SFO. These kinds of separate arrangements can complicate things even further.
Really lounge agents shouldn't have ventured the "information" when not asked, but I bet probably proffered it trying to be helpful.
What's that occam's razor theory again? That the simplest explanation is usually the right one? Agents trying to be helpful to the passenger, but having wrong inforatmion. That doesn't have to mean it's deliberate or an edict from the company.