Agreeing with kayty.
I would be interested in what body of knowledge they are using to teach from (Denny's book/Cavalry Manual/complilation). Where is about common sense/teaching for purpose?
Let's talk about general alignment, and then what happens when the feet torque. First there is ear/shoulder/hip/heel in alignment and upper arm as part of trunk. With the longer leg (riding on the flat)and having the foot more parallel, heel lowered, it is then possible to open the hip more and have elasticity in all three joints; and that means the entire leg will 'adheed' better to the horse, making sitting easier. Over fences, the rider is more in a 'light seat' (slightly ifv) because the horse is moving at speed, the center of gravity is further forward. To allow this, the stirrups are shorter, there is a sort of tripod created by the leg to allow the rider to be in two point/balance position, the thigh/calf is more secure with a little less of the spine of the boot being on the horse. But, it is not turning the toes out per se, but allowing more security in the leg (NOT pinching). The rider should still 'feather' into the heel but never pushed them forward to do so. To find the 'right place' in proper two point, just have the rider put the lower leg too far back (they will fall forward), and then too far forward (they will fall back), then find the middle point.
As far as where the leg is: the inside leg is closer to the girth (sometimes pulsing actively) and the outside is stretched back and down from hip to heel (passively...NOT actively).
Are the five rein effects really not being taught??? I wonder why not? Is the suggestion 'just' a direct/opening/leading rein? Or is it a direct rein of opposition? Without an indirect rein influence the horse cannot really ever be ridden inside leg to outside rein. And it is an indirect rein which allows for a quick land/turn.
Longer/lower/chewing the reins from the hand/aka stretching is a test of the connection from leg to hand.