I think main point is that KN believes that the stock is cheap...

I think main point is that KN believes that the stock is cheap and he might even be in a position to know. Perhaps he even knows more than some of here on HC??
Why would PTM be cheap? Perhaps it relates to what KN has been saying recently. Monetary policy of central banks has flooded the market with cash and rewarded all the wrong players, distorted the market and caused asset bubbles. This has been great for zombie funds (index funds) and general market but stock pickers like KN and Warren Buffett have been wrong footed by indiscriminate buying. But things look like they are changing. Interest rates in US will go up, only a matter of time. Easy money coming to an end. Which is probably why KN thinks that now is good time move.