He loves buying companies on the cheap. Having said that he's always happy when a stocks price drops.
Accordingly he won't be rushing in to prop up USG's price. He's happy to take your shares on the cheap.
He cannot buy more shares for 3 years without hurting the NOLs, but he now owns almost 1/3 of the company and will eventually buy the rest. But to your point, no, he will not be buying on the cheap here. He cannot without hurting his large position.