The OneWorld Visit Asia fare must be sold "in conjunction" with an intercontinental OW flight.

My question: what exactly does this mean? I'd like to buy a cheap Priceline ticket on a OW carrier, then take that to a travel agent and buy a Visit Asia fare. AA PLT desk tells me it must be sold simultaneously. I'm not sure I believe this. Can anyone else shed some light on what a TA can/can't do here?

Thanks!

(Edit: I've done after-the-fact ticketing of a OW Visit Japan fare before, and the travel agent only asked for a copy of my SFO-NRT itinerary.)