I doubt whether a public super fund would be shorting pls as...

I doubt whether a public super fund would be shorting pls as most would not even have mandate or interest to even go long.
On the question of holding shares in pls and participating in the SPP. They will if you call and ask and they didn't send you an offer. Last one I did, the trustees sent me a letter to give them permission to do this. It all worked fine.
I couldn't see trustees taking your entitlements and gaining advantage. That would result in breeches of acting in the best interests of members. Doesn't bode well for the future of the fund and trustees to do that.
So if you don't receive notification from your fund, call and ask. B aware that you may need to talk to a few staff to get understanding of your request.