This is what Ben Trollin says in response... and I doubt very mucb it's as simple as he describes
"But Butler doesn’t have any offseason workout bonuses, and if he wanted to show his displeasure with the Patriots, he could skip spring practices, sign by June 15, and still collect his $3.91 million."
I'm no expert on holdouts, but I doubt very much Butler can simply sign a contract and collect a paycheck. Teams can fine players for failing to appear for workouts, training camp, and games, and I doubt very much Butler wants to take this that far, and risk losing what little he stands to earn