Thanks for the info, everyone.
If the neutral has to be insulated from a subpanel, wouldn't there always be a separate grounding conductor in the cable, so you'd always end up running a total of 4 conductors from the subpanel? Since you'd always have the separate neutral and ground conductors, the only real reason to put a 3-wire receptacle fed from a subpanel would be to avoid changing the appliance cord, which I assume was the reason in this case.
Brian
