If they owned that much of NOT or others they become a technical insider based on ownership % alone and we would be aware of same.
As to the large volume of trading, there are a hundred reasons why people move shares around between related or allied interests, through the exchange. We seem to be obsessed on the forum about clandestine activity, but that is the least likely reason for the volume.
With drilling results ahead, some are possibly taking tax losses with a view to reacquisition after 30 days but ahead of results, just an example. Others could be moves between funds. It would bear more scrutiny if there were significant price swings, which there are not. If people think we are at a bottom, there will be some shuffling . If it were someone else digging in for a toehold, you will know soon and of course that would be quite positive. I'd hate to think that CLF or VALE or someone (anyone?) is not interested. But these do not look like bids where the seller was not known to the (presumably pre-arranged) buyer. All of which is neutral to positive for us long term holders.