It really puzzles me how this is helping and how it was done?

Does it make text more clear? How exactly? Does the German language is more descriptive? Does it somehow expands context?

So many questions in this fun fact.

I wonder how they came up with that. Was it a human idea, or did the AI stumble upon it?

Given that it was inside a 9-step text preprocessing pipeline, it would be surprising if the AI had that much autonomy.

I think it's fairly known among "LLM practitioners" (or what to call it), that some languages are better at solving specific tasks. Generally if you find yourself in a domain dominated by research in language X, shifting your prompts to that language will give you better results.