I actually once developed two sheets of 4x5 film in PMK (maybe it was the original Pyrocat) and put one into a water rinse instead of stop bath, and the other went into Kodak Indicator Stop Bath. They then were fixed together. The sheet through the water bath was about 0.01 density units higher than the one in the Indicator Stop Bath. I atribute the difference to just random error of the densitometer, or perhaps the water bathed film continued development for just a few second more than the stop bath film.
But I hope this shows that pH of the stop has little effect on the pyro stain.
I suspect that the pH of the fixer has little effect as well.