Mine (S&SS CRS & CBS) breed like guppies at a pH of 7. My KH stays between 1-2, GH 5-6. Temp 71-76. Heavily planted, in fluorite. I just sold my colony down from about 300 shrimp. I use RO and am about as unconventional in my method of adding back minerals as they get. Some sea salt, liquid calcium chloride and a touch of flourish. Acclimation, maintaining a consistent environment and minimizing bacterial pathogens while providing a nourishing food source is what I would say is key. I even have one I think might be a wine shrimp that was born in my tank.
As to the pH of 8, there is a subset of breeders that argue for alkaline water in breeding these shrimp. They feel that one of the reasons some breeders stock is so sensitive to pathogens is that the acidic water pits the shells and allows entry by bacteria. I don't see the point in constantly buffering my tank one way or another if they are thriving at the point that the tank naturally wants to sit, but this is by far not the first I have heard of high pH breeding.