I looked into it too! As I showed above, the 5W-40 is described in the Taiwanese site to be specced for the Mercedes, VW and Porsche A40. I believe this is the 'M Formula' or 'European Car Formula' sold in the states. The first link I gave
is a US site and talks about Porsche A40, Mercedes etc etc.
However, if you go to sales, the Porsche reference drops out of the picture! If you chase the 0W-40 formulation, you see the Mercedes alongside the Porsche spec. Strange!...
Personally, I wouldn't worry about it, I would tell the mechanic not to do it again and use 0W-40 or else... I can see an indie servicing Mercedes, Porsche and exotics buying 5W-40 by the 55 gallon drum and using it indiscriminately, and I wouldn't bellyache too much. Just see whether they may have a 55 gallon drum of 0W-40...
But... I live in Houston!...

0W?
