I may be wrong, but I believe I read somewhere the maintenance card calls for the removal of the DP to access the vent/fill hole. I agree its not really necessary but some places will stick to the card to avoid getting sued down the road. I am NOT taking up for AAMCO just adding context.
According them they "couldnt find anything about how to do it so we have to take the exhaust off" lol not too big of a deal, I'm sure they just wanted to take every precaution