I just ran another test - dark room, camera set to ISO 100, f/22, 5 seconds exposure, +3 flash compensation. Triggering the strobe via on-camera flash produced an underexposed image, but triggering it with my cellphone's LED flash (that's what the five second exposure is for - open the camera shutter, then trigger the ST-100 by taking a forced-flash photo on the phone with the fiber optic held up to its flash LED) produced a noticeably brighter exposure. While I can't quantify it, this does confirm that the strobe's maximum power output is held back by the triggering bulb's pulse duration.
I have contacted Meikon support, and they have offered to replace the strobes, but right now I don't see the point of shipping them back and forth again as with six different strobes exhibiting the same behavior, this appears to be a design issue rather than a manufacturing defect. I have explained the problem, linking your video and davec13o2's oscilloscope results as additional proof - let's see what they have to say. Maybe a miracle happens and they redesign the optical trigger circuit and replace all of our strobes? I know that an early batch of A6xxx Salted Line housings had an issue where they leaked between 5 and 10 meters, and they replaced those quickly and at no cost.