What?
Gt Obach; I see what you're saying; the edge is a 3 layer sandwich that runs all the way around......
I'm not trying to go too far out on a limb and say that butt welds are intrinsically weak; I'm only saying that they have been described that way in instruction books for working blacksmiths and such view also seems to obtain in a variety of cultural settings, where the buttweld is not used. Part of this (in the case of interpretting physical culture; the books explain themselves) may be cultural/paradigmatic to do with geometry and/or metal production; the idea of a flat edge, with which to make a butt joint, seems fairly naturally occurring to industrial people, but it's actually a thing that must be deliberately produced, just as wood comes in flat boards in industrial culture, while in traditional culture, it tends to come in trees.
Part of it, as explained in the books, and as many of us can testify from experience with antiques, while various professional welders have always asserted that a good weld is as strong as the solid metal, is that bad areas in welds were routine and though avoided, were often assumed/allowed for in design. Not only that, but it seems to me that when laminated objects break, they do sometimes tend to break by delaminating, and this seems to happen where they were previously solidly laminated sometimes.
The old books generally imply that a weld can seem solid but have basically microscopic cold shuts throughout it. So, while a good weld may well be as strong as the metal (as logic would certainly dictate) it seems that it could be in many cultures considered perhaps overconfident for a smith to rely excessively on the quality of his weld, when he could have improved it by expanding its quantity across a wide scarfed joint (BTW, AFAIK a scarfed joint is one where the two pieces come together at a slanted surface, thus lengthening the joint; this technique has many varieties and is prominantly used in laminating metal blades, but also in carpentry, for instance, and leatherwork; anywhere two things are being adhered, I guess.....).
I've no doubt that some welding technologies have been better than others, and so may more justify reliance on butt joints. As I have said, butted edges are seen in the swords of many nations (Including in Europe, although inlaid edges are also seen Europe, formerly on fighting swords, commonly up to wwII and still on some of the more expensive tools. The butted edge is archaic in Europe, AFAIK, which is no comment on quality; I'm just pointing out that although seen in Europe at certain times and places, it is not the European standard, which modernly is either an inlaid edge [or in N America differential hardening] or a spring tempered blade, I'd say.).
Of all the cultures whose welded blades I've seen multiple examples of I think I've seen welding flaws from all of them. And that, of course, means there were other internal flaws I did not see. Europe, Africa, Tartar/Indo-Persian (nasty long cold shut inside the applied spine of a pesh kabz
), SE Asian, Japan; it could happen in any country......