Hence my disclaimer at the bottom of the post.
Lufthansa throw anything from a B737 to A321 on the FRA/MUC flights, which often varies from what they load in advance in the timetable.
So, while the MUC nightstopper is scheduled as A320, the reality is that the A319/A321 can appear.
The point of my post was that larger equipment was scheduled across the board.