Been using blag gold for years, started with coco, went to sunshine mix#4, now BG. I believe its soil, I haven't ph'd in years. Soil acts as a buffer or some such.I know, it depends on your local water source, yada,yada.
Sometimes the rain here is at 6.0, sometimes it's been as high as 9.0, and the garden still grows fine. I quit ph'ing in soil since I discovered that, never made a difference since.