The broker report only shows volumes via each stockbrokers, not showing any underlying holders.
UBS net buy volume on AVZ, was mainly from Rare Earth ETF.
I don't think UBS volume on PLS was from Rare Earth ETF as the Rare Earth ETF bought PLS a while ago, but they bought AVZ at around 30c just in March 2018.
Here's the change on the top 20 shareholders between 15 - 31 May 2018: