Finally got around to testing this...Put your VOM across the battery terminals and then retry the test (RPM). Best if your meter has a dial vs digital, but beggars can't be choosy. Does the voltage fluctuate when the headlight dims?
Now measure across the terminals of the bulb (inserted into socket and working) and retest. Same voltage? Measure the socket where the bulb inserts into (no bulb) Still fluctuating?
I wonder if it is a voltage regulator issue. Assuming our bikes have one...
So same as before, was 14.24v at battery with raised rpm.
The interesting part was 8v at bulb with lamp on and 18v ?! at connector with no bulb?
I wasn't able to check if revving it had any effect, not enough hands.
Bottom line, swapped back to LED. Same bulb but different driver. I tried the old setup again, still no low beam, then swapped a new driver and low beam on the old LED bulb worked. Old driver was noticeably warm when I pulled it, so that must have been defective.
LED bulb is unaffected by rpm, just wicked bright all the time.