Another mystery that likely will never get an answer is what was the point of departure between the OTU timeline (now overwritten by Mongoose Charted Space timeline) and the GT ATU timeline. Loren always said he would one day reveal it. He never did.
To a certain degree, this doesn't really matter: the point of departure of the LTU from the OTU is below the resolution of the setting, so it's enough to know that GURPS indicates it in its core book when it has a TNS entry noting the explosion of Dulinor's craft.
Close enough, I say, and there's more important things to bother with: namely, when they can inflect, and my money is on 1450.