I don't think we'll ever know why some makers signed their guns and others didn't. Or even why in some areas, say Lancaster, where a number of makers seemed to have signed, or in Reading where almost none did...
As for the AH guns, I don't believe anyone is contesting that Adam Haymaker was the maker, nor am I grasping the importance of whether one or both might have been Haymakers personal guns at some point, or the AH simply his signature as maker.
As to which gun some guy had in hand when he was killed in 1774 is probably impossible to prove beyond question at this late date, without a document describing the gun in very fine and exacting detail, especially given the similarity of these two rifles.
But Jesse, if you have the documents and your satisfied that they prove the point, it's your story and that's all that counts, so stick with it!