I'm afraid I won't be much help in explaining it. I realize that the graph they show is the result of many measurements of many photons, one measurement per photon. I have absolutely no idea why it works the way it does. I do tend to agree with you about which explanation to go with, Number 2, an explanation that hasn't been developed yet.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.