F1 does stand for forcing for one round, and that's exactly what it means. It's often used in describing a forcing NT, when opener's non-jump rebid is non forcing. SAYC describes a 2/1 response (1S-2C) as promising a rebid, which is not the same thing as forcing for one round, since it follows that opener's rebid may not be passed. Other ways of playing 1S-2C include forcing to 2NT. Each is different from the other, and means exactly what it says.