Yes, and this case is between American parties, under American law, in the U.S. (of America) District Court for the Northern District of California.
My boss could fire me for disliking the color of my T-Shirt this morning.
Every decision to choose one course of action over another is "discrimination-based"; you mean as long as it is not discrimination on an expressly-prohibited basis.
This is an American case, and it's being litigated in accordance with American law, so the judge is using American rules about employment to achieve the goal here. I would be surprised if there weren't some way to accomplish the same goal in Germany.
Regarding discovery, I must say that the US system is actually more advanced than Germany, where, in civil law, there isn't really a doctrine for recovering incriminating evidence (or otherwise compelling evidence) from the opposite side, apart from a few specific circumstances.