I agree with a heck of a lot of the above (especially the comment about nomenclature) but we almost certainly would not be having this discussion if a simple agreement had been reached by the crew as to when the published procedure permitted leaving 2500' and what NBD indications were required. Regardless of what mode the aircraft was navigating in laterally, this was an NDB approach.
I do accept that workload/SA wasn't helped by the modes used and there may have been restrictions on modes available...