Doesn't need to be simultaneous. This summer, I booked a oneworld award to Asia, then -- weeks later -- booked my Visit Asia pass.

The only timing requirement is that the first and last segments of the Visit Asia itinerary must fall within your Asian arrival and departures dates on the other itinerary.

BTW: My Visit Asia itinerary was not complex, and the ExPlat desk got it setup rather quickly once the agent did a quick refresher of the VA rules.