One thing I wonder about doing things like this: the more we increase the height we raise our foot to in the abductor strengthening movement, that muscle is shortening and we deal with over-active insufficiency challenge. Conversely, when we train adductor flies, the lower we bring our feet, the muscle is lengthening and we deal with under-active insufficiency challenge.
What it makes me wonder is, should we be doing a movement to stretch the abductors? The problem is that the thighs get in each other's way so it seems that to adduct past neutral position to do a stretched abductor movement, you need to either abduct the other thigh or else splay them (one thigh flexed the other extended) to clear room to go further.
Rather than visualizing it this way, another is with hip tilt. Like for example, if we lead a leg raise to the side with our abductors by tilting our kicking leg's up up first (easy way to learn this: keep feet flat and lift 1 leg off the ground) this would pre-stretch the abductor and give a wider range of movement.
Conversely, since this is one way the foot gains height, we might get a false sense of how high 1 leg can raise via its own flexibility with both hips are contributing. Best example of this is how for a back kick, most people's motion comes from flexion of the base leg rather than extension of kicking leg.
