Bill,
I think that a formal interpretation requires the involvement of the CMP that covers the section of the code(I'm not sure about this, maybe Joe T. and tell us for sure how an interpretation works). The people that write the Handbook are not the people that wrote the code, the code making panel members write the code. The panel members are not employees of the NFPA, but the authors of the handbook often are. The statement in the handbook even says it is not an offical interpretation because the writing of the opinions in the handbook do not follow the rules in the NFPA Regulations Governing Committee Projects as would be required for a Formal Interpretation.
In my opinion the best place to find out what the CMP is trying to say is to look at the Report on Proposals and the Report on Comments for when the section in question was added or changed. Even panel statements on rejected proposals for the section in question will often give an insight to what the CMP thinks the code section actually means.
