I don' t believe captive pivoting limb pockets give peak efficiency, but they do provide for better " tightness of tolerances" vs. having loosened limb bolts in fixed pockets.

I' d be curious to grab some of our high-speed video equipment from here at work and film a fixed limb pocket, 60-70# bow that has been back off to the minimum of 60#' s and see if the limbs ends in the pockets ever " bounce" away from the limb bolt heads during the shot process......

I' ve always been a fan of the pivoting pockets myself.