Thanks Var! Very interesting.
So the original H50 was 120 degrees (although there was a rare H50b variant with 80 degrees), then the H501 narrowed down to 80, and H502 goes back up to 120 again. Yet the difference is jolting in your wall shots. The H501 appears more even across its entire spread, but if you examine the central portion of the H502, the evenly lit portion appears just as large as the H501, then adds a falloff area around it.
My issue when working in crawlspaces and attics is that tools go "missing" in the dark, so this extra wide beam should be very handy. Just conjecture based on your photos, but the H502's beam would seem ridiculously large for trail hiking. One problem with a very wide beam: it'll light up nearby objects and temporarily "blind" you with the reflected light. This happens to me often when using my SD52 in attics...I'll get near a joist and that ultra wide beam will reflect off it, constricting my pupil temporarily. Generally worth the tradeoff of being able to "see everything" when working, however. But could get annoying if you're going through brush or low hanging branches in the wild.
Having seen these photos, and being aware of how many people want their headlamps for night hiking use, I'm wondering if an H502 will be issued in a "b" version, a la the H50--ie, a full flood of 80-60 degrees in width. I imagine something like a simple lens would do it. (Although the H51f should have that sufficiently covered? Don't own one, don't know.)
Of course, if ZL would have just threaded that bezel...
PS: Yes, the H502 would be great for "DavidT Carry" (around the neck, under the shirt). When I carry my H501 that way I notice I spend more time than usual adjusting the beam. Neck carry needs a really wide beam.