At that point it sounds easier to have the focus switch executed automatically with all relevant parameters preset, e.g. duration or curve. Sort of like CSS transition or MIDI automation.
Back then the focus puller would use a remote connected by a cable, which is why you see a focus puller running behind the steadicam op in that video.
That's why while you've got A/B points set and marks set on the focus control, you still need a human.