DB is weird. They seem to make their own rules and then run the game and “dont tell the rules to anyone”. I was on my way to catch a flight from Munich to my home (Madrid). I didn’t knew that apparently at one point the train splits into two parts and the front part goes to the airport and the other part just goes to the nearby cattle farms and comes back in 3 hours. Google Maps - No idea Citymapper - what? English a…
That is indicated on the platform screens before getting on the train. It tells you which part of the train goes where so you know which wagon to take.
I found it also not very intuitive first time I took it. But hey, when travelling there’s always local peculiarities to take care of ;)