Read the standard.

Having read the standard and seeing manfacturers offering refer to "a contrahelical wire can be applied per customer request" before posing the question. In South Africa a split concentric is applied with SZ operation and therefore pose the question again by asking is the rule for helical application of the concentric neutral rigidly applied in North America region? Yes or No would be a good answer.

I did not understand your question: the main conductor is it SZ [True concentric] stranded or the concentric neutral is it two layers SZ stranded? The two layers of

concentric neutral could be one layer neutral and one layer insulation shield. Could you be more specific, pls.?

main conductor true concentric, insulation, bare copper wire neutral ( full equivalent to main conductor or 1/3 neutral) applied helically,wires equally spaced or as per question SZ application of bare neutral permitted?

I have not ICEA S-94-649 with me, but if I well interpret your sentence "a contrahelical wire can be applied per customer request" that means SZ configuration.

I think also one layer of concentric wire it is, some time, difficult to achieve. So the answer has to be "yes" [it has to be permitted].