Yes, this is likely an artifact of how their systems are setup. I was booking an award ticket for a friend SYD-HKG-TPE, and the AA agent was asking for the same information. I did mention this was on a non-US carrier 6000 miles away from the US, but she replied, "This is part of the new security as of about a year ago." I didn't try to argue the point further and just gave the information. Again, it's the US carrier booking systems being unable to support decoupling US and non-US flights. Typically, you would be booking a flight including a US segment when using them, even for award travel.

I imagine it would likely be a dummy field, even if the name is run through the Secure Flight database. That is to say, the partner airline probably wouldn't even have the information sent to them if something came up. Also, once the itinerary has been ticketed, you can get the booking number for the partner airline and deal with the reservation directly on their system.