Yep, don't know what the answer is really. Legs tend get dirty quickly and any labelling either gets covered in dirt or worn away over time.
Even if you had 4 different part numbers someone would still end up fitting No1 transducer to No2 wheel if the wiring was crossed.
Should never happen so long as the MM reference is clear (I believe it is in this case) and that same MM is followed.
Perhaps a software change in the BSCU could be made that would detect the wrong brake is being released? Not sure if that would be possible.
p.s. Different loom lengths wouldn't work either as the harness runs down the centre of the leg before splitting off down each axle , each axle being the same length.