I refer to your interesting lesson on latin hip motion.
For the application of this hip motion, you refer to rumba, cha cha and mambo. Haven't you forgotten Jive ?
On an exam I was asked to explain hip motion in jive. On which counts do you have hip motion: 1 2 3a4 3a4 ? I am (quite) sure (although) about counts 1, 2 and 4. But what about counts 3a ? And how do you compare hip motion in jive with the one in cha cha ? On the exam I recalled something about a "delayed merengue hip" versus a "straight cha cha hip" but mentioning these in relation to jive got me even more confused.
And now I wonder also: is there no hip motion in samba ? Or is it less pronounced ?
In Jive, the hip action occurs on counts 1, 2, 4, and 6 (assuming that 1,2 is the rock step). The rock step on 1 and 2 uses an action similar to American style hip and [bent] leg action. The 3a and the 5a have the hips basically neutral, with a slight flex in both knees. 4 and 6 use more of a side-to-side hip swing than a rotational hip settling action.
Cha Cha's triple is smoother and level. The hips move in a rotational manner as outlined in the lesson, but the action is much more subtle, and not necessarily guided by the alternation of bent-straight action. In fact, the generally accepted technique has both legs straightening simoultaneously on the 4 and the 1 count, and both bending simoultaneously on the "&" count in between.
Jive's action, in contrast, is more rhyhmical with a slight bounce. The knees are bent on the 3 and the "&" and also on the first part of the 4, strightening only after the weight is transferred to 4. The hip swings sideways (not rotationally) on the end of 4 as the standing leg straightens.
There's definitely a hip action in Samba. I wouldn't call it subtle, either, but then I guess it depends on what step you're referring to. Most actions like Samba Walks, Botafogos and Voltas all use a very strong hip action. The leg action differs from Cha Cha/Rumba in that your weight lands on a bent leg.
I hope this helps. Future lessons, of course, will go into more detail with all of this stuff.