I’ve seen your excellent pictures but it is difficiult to say IMO if these are completely flat with cutting sharp edges. Polishing in a modulated groove must include different angles and variying contact patch area as opposed to a stationary unmodulated groove. I can’t see it happening unless someone left it running in the runout groove.
I can now say for sure, having viewed maybe 50 or so random old styli from my scavenged cart/stylus boxes of various vintages and usage in the last week, that the wear does indeed present itself as very obvious flat areas with very sharp edges to the flat spots. It is trivial to see uneven wear caused by faulty/incorrect antiskate (more common than I would have expected).
I have been using my various optical scopes, with movable/fixed lateral slightly elevated diffuse lights. There is no need to go esoteric or lash out on a SEK-2, x150 to x200 on my trusty Olympus scope shows all the detail I will ever need.
I have some wonderfully worn, new and lightly used identical AT conical styli which demonstrate the textbook perfect Shure 'cat's eyes' in various stages right up to an almost flat screwdriver type heavily worn profile when viewed from directly above. Once seen, it cannot be unseen and it's much better to skip the cat's eye reflection and view directly with diffuse light, the flat wear surfaces themselves. What is also clear, is many of the salvaged styli and carts I pulled of stripped tables over the decades were in perfect condition. Others were heavily worn. Age had nothing to do with it. A V15 III original supertrack plus stylus from the mid 1970s appears unused with not even a tiny patch of wear.
As I don't really care for preserving my various test records, I think I'll try say 6 or 8 identical, but variably worn AT conicals ('cos I have a pile of them) for distortion, starting with the NOS styli and working back to the worst worn to see how bad THD becomes.