Hi Max, I am not good with technical jargon, or even particularly knowlegeable about the subject, but I also wondered about the TA/pH "thing".
Given that the pH number system has already "translated" proton concentration to a simple scale of 0 to 14. Then TA calculation is done using specific chemicals which change colour within a certain acidity or base range specific to that particular chemical. So I would think that the shades
between the upper and lower limit of that range COULD be allocated their own pH number. Also if one used various available indicator chemicals right up the range, and allocated those same pH numbers appropriately to every colour shade in every (overlapping) indicator, greater precision and accuracy could be attained too.
It all seemed so clear to me when I started to write this... oh dear...