A Toyota exhaust - or any car exhaust - is assembled from more than one piece, and pattern replacements are made to join to the original parts. Maybe they rounded off the bolts trying to undo them and made up an excuse!
Not true.
The exhaust on the Clio 172s (not sure on the 182s) is one piece from the factory, as in it's not 2 or 3 sections bolted together. It's one long welded piece.
Then when the back box inevitably goes you have to buy the replacement in 2 sections. Reason being at the factory the exhaust is put on before some of the other bits that normally would block putting it all on as a one piece