https://web.archive.org/web/20160723102129/http://www.arch.ksu.edu/seamon/fajans.htm

These Berkeley Professors bring up an interesting idea. Not so much mentioning safety directly. But they mention 2 different possible routes, one with more stop signs and one with more traffic and fewer stops.

While a drop of a few miles per hour may not seem like much to a car driver, think of it this way: the equivalent in a car would be a drop from 60 to 45 mph. Because the extra effort required on California is so frustrating, both physically and psychologically, many cyclists prefer Sacramento to California, despite safety concerns. They ride California, the official bike route, only when traffic on Sacramento gets too scary.

So perhaps adding "stop as yield" changes the calculation for what is the fastest route by bicycle. Which leads bicycles to take safer routes with more stop signs and fewer cars. That could explain some of the decrease in accidents when states/cities pass these laws. Change in bicyclist behavior.