Etoro swap strategy?

They have extreme rollover, charge way more than almost any other broker, up to 3 times, and pay way less, about 50% than solid brokers like fxpro.

Some time ago they introduced some new pairs and 1 is rather odd. Shorting GBPNZD pays the highest rollover in the market so I asked one of their employees via email:

[I]I have one question about a really odd thing that I’m wondering about since Etoro brought some new pairs a while ago.
As we both know Etoro makes insane money from swap because they charge way more and pay way less than well known brokers that attract the traders with the big accounts.

However… GBPNZD short has the highest rollover in the market, check forexchurch yourself if you like.
Why?
Is this some weird mistake or is Etoro just waiting for enough people to short the pair and after that lower it dramatically when the required volume is reached so they are sure that also this pair will bring them a lot of money on swap only. That seems to me the only logical explenation and in case anyone says otherwise I would even bet my house on it that at some point that rollover will at least be halved this very year without central banks changing interest rates.

Or maybe you can explain me the reason of this supernatural phenomenum?[/I]

This can be the one and only reason or am I missing something here?