Rookie camp is optional, whereas I believe he's contractually obligated to show up to main camp. If he's threatening to not show up to main camp, even if it's a bluff, you can bet he's definitely not showing up to anything he's not contractually obligated to.
I still don't understand the posturing, though. His best shot at getting what he wants is to light the world on fire in preseason. Either he earns a spot out of camp, and he's on an NHL roster like he wants, or he shows another team that he's NHL-ready, and they pony up the assets to acquire him.
Still, it's quite telling that Jones, Robertston, Emberson, Pajuniemi, and Khodorenko are all coming to Rookie camp without (public) complaint, but Nils, who really proved nothing during his time in Hartford, is absent.