I wouldn't be in much of a hurry to extend most guys these days, either, especially pitchers. It seems like the deals being made with arb-eligible pitchers are either (a) guys who are getting really close to FA, like Cain, or (b) pitchers who are willing to give the team discounted club options to minimize the number of FA years a team is risking.
Maybe JZ is unwilling to give the team a couple of options on the back end, who knows? If he was willing to sign a 5/$35 that turned into a 7/$60 or something like that with a couple team options on the backend, the Nats would be fools to turn it down. But we don't know that's the case.