Going through various ATGS posts from the time, by all indications, FF '94 WAS on the same contract as TPiR.
Four possibilites, at least that I see, really exist here:
A) GSN got a sepearate lease, one-time lease, for this one episode
B)People have been wrong about the issue of them being on the same contract CONSISTENTLY throughout virtually the entire history of the group
C)GSN picked back up the TPiR/FF '94 contract
D)Someone was asleep at the wheel, and let air an episode they currently don't have contractual rights to