It's a Fo1 vanilla encounter. /Edit: Actually this is an ages old addition of TeamX - the original merchant would always decline your request of traveling with him. However, the dialog options are in the vanilla game, which is likely why TeamX implemented the feature. It became part of Fixt later, which is why it's also in et Tu. Personally I don't mind it... oh, but I fixed it, because it was semi-broken (/edit2: Actually it's semi-broken in v1.0 as well, because of a rare crash-fix I've implemented one or two days before release. Traveling with the caravans will take A LOT more time than it should. It'll be 100% fixed in v1.1). Didn't know they would appear as far north as Shady Sands. Maybe I should add a condition to them, so the ones high up won't be able to bring you far down to the Boneyard. Though I actually don't think it bothers me that much.