As a rule, when I say things like "there is no evidence that such-and-such existed before this time", I am expressing, not a personal opinion, but my understanding of the general consensus among experts (of which I am not one) who, unlike me, have studied the subject in some depth. As it happens, I read the Cass/Roud book only a few weeks ago (a review copy; I do get just the occasional perk) so the current state of thought on the subject as summarized there was fairly fresh in my mind. That doesn't mean that what I, or anyone else says, is necessarily right; just that, given the present state of knowledge, it is the most likely case. There may well have been earlier forms of mummers' play, perhaps involving death and resurrection, but we don't know about them, so we can't assume that just because it would be nice.

The presence of analogous practices in other countries doesn't in itself say anything about the practice here, where the basic play text seems to have spread via chapbooks and seems to have grown considerably in popularity through that medium; on the other hand, "new" old material relating to traditional pursuits comes to light from time to time and may well do in this case, at which point a re-assessment of the current working hypotheses will be made.

I don't see any "logical trap" there, but I'm quite willing to admit that at times I may express myself a little over-emphatically, though this is perhaps necessary when dealing with "folklore about folklore", where often-repeated assumptions (some demonstrably false, others just unsubstantiated) tend in time to assume the weight in people's minds of actual evidence. Perhaps I should include more caveats, but that might lead to unwieldiness in an already over-elaborate sentence structure...!