I meant to say landing/taking off with an internal rotation of the feet where the toes are pointed towards each other and closer than the heels. I mean this in general for anytime you are landing or taking off. This leads to knee injuries.
That part is really a shooting technique thing. Since you rotate the hip to enable the shooting shoulder to be aligned towards the hoop, it makes sense to roatate your foot since your aim is to have as little tension as possible so balance is at its peak. The toes pointing towards each other is a result of how you "break", keep momentum. You do the 1-2 usually out of a dribble motion or in a situation where you want attacking a close-out to be a possibility, so your trail foot's toes are pointing towards the hoop. When you 1-2 step into a 3 the decision to actually shoot and not use the 2nd step as the gather step and continue dribbling the ball is a split second thing, where you either align the lead foot in the direction you wanna move or you use it to adjust your body towards the hoop for the shot and said "turn" motion happens. Since your trail foot was pointing towards the hoop, he keeps that way (pivot foot stationary) and toes are closer than heels.