I never realized it before, but even in Kirk's day I found a hint that the Enterprise could separate the saucer section and maneuver it separately, as in Picard's day. In this scene 25 minutes into The Apple, the machine god Vaal of the local tribal people is bringing the Enterprise down with some kind of tractor beam. If Scotty lets that happen, not only will he and the rest of the crew perish ("There's over four hundred guys, there!"), but Kirk threatens to fire him.
Scotty (on the bridge): ...We're goin' down and we can't stop it.
Kirk (on the planet): I'm sick of hearing that word, "can't!" Get that ship outta there.
Scotty: Sir, we're doing everything within Engineering reason.
Kirk (furious): Then use your imagination! Tie every ounce of power the ship has into the impulse engines. Discard the warp drive nacelles if you have to and -- track outta there with the main section, but get that ship outta there!
V a a l