Syempre if something is done wrong, bumababa ang durability.
Then there's also the pedal itself. Boss and Boston pedals are so nice to modify because matitibay ang boards nila. On the other hand and ironically, Marshall pedals have such fragile boards that the chance of stripping the foil is high if you don't wield your soldering iron gingerly.
So yes, that "can" be true, but not to the general extent to cause concern. That's assuming that the guy modding really knows his iron well