Again, it is because BA classify all German flights as band 2 catering (competition of course LH also only offer cold plate.)
It is a case of how little BA can get away with.....
Compare LON - NCE with HOT catering(Band 3) at meal times (choice) even if it is 35c in the sun....
LON -MUC or TXL - Salad..... (band 2) even if it is a freezing dark January evening....... You couldn't make it up

I have experienced both and the flight time was 30 mins longer back from TXL than NCE!!!