I found the statement from the non-technical rep on their forum-- " FerreX has a special blend of surfactants which makes it work better than solvents in removing wax and tar."
You know Dr. G is a polymer wizard (well, at least to us laymen) so maybe he threw that in to assist in the iron removal and it has some minor tar removal properties so they added it to the label blurb. It's probably better as you noted to separate out the two tasks (although if I ever get to use my Trix maybe I'll change my mind).
Since we're talking about storm drains and surface water contamination, the thioglycolates can't be very good for the fish, either.
I realise Dr G is an expert but the truth is that there is only so much that you can do. Like it or not, to hit the price points that are needed, Optimum are using the same sort of surfactants as the rest of us. They can blend them differently and may get synergy but they won't have the luxury of manufacturing a specialist surfactant that is unique to them, that is big chemistry and (unless i am missing a parent corporation) beyond the scope of detailing brands. What they may be referring to is the 'bug and tar' remover type products which are found in the US. Most (not all) are not particularly high solvent products and, being brutally honest, are useless if you have any real amount of tar. It is quite plausible that Optimum may have compared with these products and rightly found tar removal to be superior. Interestingly, Optimum choose not to name any surfactant components on their safety information. In this age of the globally harmonised system, I find this very unusual as the vast majority of surfactants are considered hazardous and thus should be noted on a data sheet, unless they are present in very small amounts.
All that said, I would love to be wrong. If someone can show me Ferrex causing a globule of hardened tar 'bleeding' the way a heavy solvent product will cause, I may well change my view!
Thioglycolates and drainage systems - I believe that thioglycolates are very good in their biodegradability so this should not be a concern. As I have said previously, many surfactants are very bad for the environment because they do not break down easily at all. I am speculating but I suspect that the EU has taken the stance of banning the use of these whilst the US has not. In place of this ban, the US continues to use these chemicals, instead choosing to ban users from putting the run off into storm drains. Personally I prefer the EU approach as we get freedom to wash our vehicles when and where we want, albeit we have to compromise on our ingredients (which, to some extent, forces development of new alternatives).