"cleaning in muriatic acid" and "restoring" probably should not be used in the same paragraph !!
I haven't seen the episode BUT I would imagine the whole point is to eat away any of the corosion/pits - which will leave clean ... pits!
Those pits are then filled - usually with solder since anything else either won't take plating OR requires more heat than the zinc emblem can tolerate.
My guess is they don't trust the plater to do a proper prep job OR they now have so much stinkin' money they do plating in-house.
I see no reason why you'd want to dip good chrome in muriatic acid !!