In waltz you basically can stop at the top of the rise without altering the technique because you very nearly do so when ordinarily dancing, but in foxtrot you must alter the technique to stop at the top of the rise. Not as much as you would have to alter it to stop at the bottom though!
A setp in the swing dances is defined as two half (leg) swings, yes - but a step in the swing dances can essentially never stand on its own - it must be preceded and followed by movement (unless its a decorative little trick not using the characteristic movement technique). Even if you were to stop at the peak of rise in waltz, you are not stopping between steps but actually within the 3rd step, so it must still have a preceding action and a following one - when you get around to finishing it.