... given the personality types drawn to those 3 Ajahs, and the more obvious need for strength re the typical activities performed by their members. That would rule out Siuan (as, IMHO, would the original comment that it's an old-school, and old, AS).

I think it's less likely to be a Yellow too, since strength is often useful when Healing.

It seems to me more likely to be a Write, Brown, or Grey. Terez' comment that the reason is rare / not general implies that there is something peculiar about the specific AS (more than just her Ajah choice) at work here. But I would think "peculiar" AS would be drawn to White/Brown/Grey more so than to the other Ajahs, so I'm still inclined to look amongst those 3 Ajahs first.