Hair consist mostly of protein called keratin, which has high content of amino acids capable of ion exchange. Thus, in theory, glutamic and aspartic acid residues in keratin can be present in their acidic (-COOH) or salt forms (-COONa or -COOK, for example), etc. So nothing wrong with this "pH balance" thingy, although I've no idea how important this is for hair quality. I'm skeptical for another reason: all these shampoos and conditioners contain ingredients that can be poisonous to marine life, so I am against using them on liveaboards and isolated tropical islands where they get straight into sea waters after use.