If you believe 240.4(D) is overload protection as opposed to short circuit protection, it clearly applies to the neutral. What goes in comes out the other end according to Mr Kirchoff.
I agree that it also includes the neutral, but even the NEC’s own description of a branch circuit could be seen as a little vague.
Art.100 defines a branch circuit is defined as “the circuit conductors between the final overcurrent device protecting the circuit and the outlet[s].”
I think it is assumed to include a grounded [neutral] conductor, but may have been intentionaly left out since not all branch circuits use a neutral.
