Since I was still awake (at 2:30am) I had another look at Craig's Kralik-glass
website, specifically the Welz Decor Index section and the entry for "Welz Ribbed Feet".
Looks like my thoughts about the Collectors Weekly
article should not have been quite so questioning, as I guess the comment about the 16-rib form being "a marker" for Welz was actually taken from Craig's web page (or the same initial source info). But perhaps my questioning was ok, as Craig's site has the "marker" comment following the sentence about the three-ball shape, and maybe it is that which is the "marker", rather than the number of ribs?
By studying enlarged views of the examples shown in Craig's site, all of the six items shown have a 16-rib form to the ball section. So, even though I may have been a bit quick to question the 16-rib comment in the article, I come back to the interesting point about mine and Keith's vases having a 15-rib form for the ball sections.
What does it mean?