Did you notice that there is also a diffence at the other end of the knurling area ?
The knurling pattern seems considered as a protruding part, so the diameter of the bezel is smaller, like every parts that are not knurled.
palimpsest, your theory works - only if the older light's bezels were not flush with the head.
If the newer bezels are smaller, it can only be
1. (unannounced) Design change
2. different batch of bezels (new machining)