My assumption was more that this is about getting set up to provide access to Fable to US citizens. I could be mistaken in that regard.

It probably is. But I don't trust personas funders (and the US gov, btw) to only use this data in this regard.

Well, if it's (at the moment) only for verifying US citizenship for access to Fable then giving them your non-US ID won't do anything for you.