I can only find 1 reference to the loop of wire for NM. 334-30(C). It requires 12 in. loopor 6 in. of cable end available on the interior side of the finished wall for replacement. BUT... It deals with devices without a seperate box. So, it doesn't help with normal wiring methods used in most residential applications. I don't see where there is(or ever) was a requirement for the loop.