I remember being slightly surprised at this flag, the answer seems well-informed, and appears to cast doubt on a foundational assumption of the question: "This is attested by the early heretic Marcion".
One careful re-read later and I see that this is (presumably) a partial quotation of a list A, B, C... and Z, where A is the 'evidence' of the Marcion Gospel and B is the Muratorian Fragment and so on. The OP is only asking about B, and A is only quoted because it would be difficult to remove it and leave the quote making grammatical sense.
In other words I see now that you are right, the question is not about the Marcion Gospel at all and fdb's answer which only addresses A is technically not an answer (to this question), but rather a comment.
I've made a minor edit to the question to emphasize this, and converted the answer to a comment. I've also asked a new question here which is directly about part A! I'm hoping fdb will post his answer there :)
Thanks for bringing this up on meta in such a constructive way (much better than re-flagging, please never do that!), and please keep up the good work flagging, editing, asking and answering questions :)