I've been wondering the same thing.....kamagong to be frank, I think the mushrooming of my Scholberg's tang was a tad excessive. I wonder how the cutler was able to deform it so much without denting the handle (which, by the way, has no resin or wax whatsoever inside).
In order to get a tang to that state it must have been way too long and white hot. That might be a bit tough to do and you'd almost certainly see some evidence on the endcap.
Another possibility is that blob is something applied as a fix at a later date, maybe an attempt to use some sort of solder to secure it? It almost looks like a bad weld rather than a peened tang end...