We can not book AS flights directly in first class, but can book in coach and request FC from AS. It is not a waitlist, but a request to be processed and responded to by AS within a few days.

Unfortunately, AS generally does not respond yes or no and it usually requires follow up by the customer, and the agent has to call AS directly and ask for it. It is an extremely awkward and unreliable procedure, and that is why most agents will not bring it up. However, it is part of the reward if you connect from AS, no matter how many other airlines are involved in the PNR.

You can do the same with a domestic itinerary as an FS0 reward.