Im not sure we know enough to be certain. At the start, they appear to have been more experimental rather than being either a request from the casino or a requirement of the manufacturer (ie - 'today', PS uses the H&C UV on chips with house molds to satisfy gaming requirements re the manufacturers mark).
So it is possible early orders contained with and without, and it doesnt necessarily follow that a chip with UV is more recent than one without.
Not quite sure why or how so many placements/orientations/sizes of hat&cane UV occurred in the earlier days. Maybe there were various methods of application. I know that it was a separate process to the regular inlay printing.
Whereas now, the UV is consistent, because I understand the UV is simply another color in the printer - ie cartridges for Cyan, Magenta, Yellow, Black & UV, so it is printed at the same time.