Germany is much less centralised than France. 20% of the population is in Paris. Only 2% of Germans live in Berlin. It would be insanity to mindlessly copy the French model when the circumstances are so different.
> there are a lot of people who actually use the stations between, say, Berlin and Cologne
Sure, and a stop in the middle would make sense on that length of route, or alternating at which intermediate place(s) it stops. But with a stupid rule like having to stop in whatever state you pass means that you have to build rails around to avoid hitting a corner where nobody lives anyway because you'd have to stop for absolutely no reason.
Let the trains make stops and rails be laid based on, like you say, demand. Not on arbitrary border lines.
There is no such rule in Germany.
> high-speed trains need to have at least one stop in every federal state they cross
That's the system working as intended, though. People like to laugh about small cities like Montabaur or Limburg getting ICE access but it turned out that the regions benefitted a lot from that access and after two slow years the demand for high speed train access in the region exploded.
> A big impediment is the federal structure of Germany, as high-speed trains need to have at least one stop in every federal state they cross for political reasons
English is more topic-loaded: We might say "for political reasons, every high speed train in Germany..." and so on. In fact if it made any sense for the reason trains cross states to be a political one, the "for political reasons" clause would attach to "cross", not "have", where I believe this is unambiguous in German.
"for political reasons" could have been regulation, also. It happens that it isn't. For that matter "need to" carries more of a sense of obligation than I feel is truly warranted.
That all said, it's valid English and I read it to mean as the author intended.
For example the ICE from Hamburg to Berlin tomorrow at 14:35 goes directly, not stopping in Schleswig-Holstein, Mecklenburg-Vorpommern or Brandenburg.
Edit: ah I see you added an example. That settles it then, thanks!
Over 6 million people live in Berlin metro, in an 80 million country this is closer to 8%.