Because it appears the Pats never presented this "starter" contract to Jimmy at all.
According to Adam Schefter: "His contract was going to be up, and New England had made efforts to sign him, re-sign him. I think the more they talked, the more they recognized that it was going to be too difficult to re-sign him. And so rather than have him walk away after the season ends, they decided to make the move now, to trade him for a second-round draft pick."
"Made efforts to sign him" is not the same thing as "presented a contract which he then rejected." "Made efforts" and "talked" is what you say when you reached no agreement, presented nothing of substance, and decided to jettison the project and move on.