I've flown DL 98/99 many, many times (including Fri/Sun of this past weekend) and have never seen a pilot take rest time on that flight.

The SEA-JFK run doesn't seem long enough to require a crew rest...however those flights originate/terminate in PDX, and stop along the way in SEA. So, I imagine it's possible that, with a delay, a pilot originating in PDX might eventually hit a 'rest time' threshold before actually arriving at JFK.