Actually, ever since the (military) compulsory service has disappeared in France, some time ago, the quality of the services of the SHAT has proportionally decreased... On the other hand, they more and more rarely give references of the boxes that researchers will have to explore once they are at Vincennes. I was confronted with the same problem at the "Service Historique de la Marine" when I prepared my last book. Anyway, what I'd like to have access to is primary sources from the US, for the way their involvement is described in French sources is often, well, let's say,... biased.
I'm not asking for much, but only some dates of patrols, ambushes, main attacks, prisoners taken, losses.
All I know, which isn't much I must admit, comes from Scott's book.
And last but not least, if that may answer one of your questions (the one you seem to be puzzled at), my concern is the Great War from Baccarat to the Swiss border; it concerns all armies and not the AEF troops only. Yet, I consider there is still a lot to learn about the latter.
PS Thanks a lot for your hints anyway.