I've done some debugging on a multiple airport metro (LAX) to a single airport metro (OKC) in GW1 and was successful in finding all potential demand appearing as actual somewhere in the combination of route pairs (or at least close enough I didn't bother to open a bug report).
However, I have not taken on a multiple airport metro to another multiple airport metro like LAX-NYC or NYC-LON, however, in my general observations, something feels tiggered with it.. so hopefully we'll get some good investigation on it... If I remember right, I've got 5k of demand from LHR to various large Northeast US cities that's not worth flying at all even when there's potential demand at 900k+.