NECC teaches (and I strongly agree with) putting the throwing hand behind the glove for any situation where you might be throwing ("runners-on" stance). Not only does this keep the hand closer to the glove for throwing, but the throwing hand also stays with the glove when blocking.
If the throwing hand is beside the ankle, it has to travel through a lot of unprotected space when executing a block, which is a safety concern.
Hand beside the ankle is correct for the "no-runners" stance.
I like the idea of having the hand behind the glove in throwing situations as an alternative way of doing it.......but it looks to me like if you have to drop and block a pitch that hand is going to be more in the mix safety wise than beside your ankle((I have always taught to drop and block by dropping to the knees with your glove down in the 6 hole, shoulders square and slightly bent over with the chest to keep the ball down in front and notuse the off hand as to keep it out of harms way) also in this position you have both arms inside the shinguards which means its twice as likely that a foul tip will hit a body part that is unprotected .......truthfully a catcher is in the danger zone safety wise every pitch. JMHO