Just to expand on this a little more, for other than possibly a service or feeder application, is there anything that actually prevents manufactures from producing NM-B cables with reduced "neutrals" for use in branch circuits?
Such as, #12 with a #14 neutral conductor or #10 with a # 12 neutral, etc.
I seem to remember seeing some NM cables being made this way many years ago.
I can see this not being a good idea and thought there was something that required them to be the same size as the ungrounded conductors up to a certain size, but so far, I haven’t been able to find anything in the NEC or White book that indicates this.
