Having greater width toward the tip absorbs vibration and thus makes a blade better for impact cutting at the tip, increasing its effective length (for cutting) vs. a narrow tip. For an extreme dichotomy think of smallswords as compared to katzbalgers or to execution swords of the same culture. So it shows an interest in having reach for high-impact cutting. This is often seen on work blades, such as machete or bangkung.
Also, the abruptly angled division between tip and edge is seen on several varieties of East Asian swords, and is used in some East Asian martial arts as a focus point for cuts.
The idea that of Japan's cultural isolation is highly over-played. Japan has traded and warred (or piratted for whatever the difference may be) with its neighbors continuously and always, laws and declarations to the contrary.
The idea of "great cultures" from which ideas spread out, is not factually established, though it is often spoken of as fact. Chokuto, the ancient Japanese sword, had this type of tip; it seems general and ancestral to the region in some degree. If anything, katanas display a down-toned version of it, usually.
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