As I understand the matter of the chemistry involved with TF4 is that if one uses an acidic stop bath between the alkaline developer and the alkaline fixer then it would appear that the greater danger exists in neutralizing the alkaline fixer. I believe that Formulary indicates using a water bath between the developer and TF4 fixer. The major benefit of using TF4 is in eliminating the possibility of stain reduction on the negative (in film processing when using pyro developers). Some have reported this stain reduction as taking place in an acidic environment. I do use pyro and I do use a stop bath with conventional hypo (thiosulfate and bisulfite) with no apparent deleterious effects. But then, I view general stain on the negative as counter productive in that it tends to reduce negative contrast. The stain that I view as beneficial is the stain that is proportional to the negative density and in the case of ABC is not visible in the same way that PMK is. I believe that the paper manufacturer is offering suggested processing procedures based upon conventional hypo usage. At least that is my interpertation of the matter.