I there are two aspects of pH. Two developers may have the same initial pH, but one may have a greater resistance to change of pH. The reaction of silver halide to development produces the halide acid as well as metallic silver. The acid then acts to reduce the local pH of the solution, more where the exposure was greater. The reduction of pH thus reduces the local activity of the developer. That is what we count on in stand or semi-stand development to produce "compensation", allowing density to build up in shadow areas at a somewhat greater relative rate than in the highlights. The initial effect of the boric acid I added was to bring the initial pH to around 8.6, but also to reduce the local dynamic change of pH.