How did I miss this longer clip of Le Clercq in La Valse posted last May (authorized by the Balanchine Foundation?):
Fantastico! Great find, Neryssa - you get the gold star today. This looks to be the footage that was used in the documentary. The audio sounds like it was added on later - either that, or they went to some trouble to mic the piano in this presentaton footage at Jacob's Pillow, and clean things up.
The first thing I notice is how closely Le Clercq's movements correspond with the movements of the earlier "Three Fates" dance - the sharp/spikey elbows, and jarring movements that succumb to inertia, soften and fade.
When the two partners intertwine arms, the tempo of their movements is quite different from what I've seen in modern versions. Not that one way is necessarily "right", but here we get to see what was first developed with Balanchine presiding over matters. Pretty thrilling, I have to say. I'll have to watch this a number of times and give it more thought...