Companies can't fire you for unrelated speech in most of Europe, their laws doesn't protect you as much from governments but they protect speech significantly more against private corporations.

So just because US freedom of speech is limited to government doesn't mean that applies everywhere.

I still don't see how that is relevant at all between Apple and Epic...

This is Apple retaliating for Epic criticizing them. You aren't allowed to do that without a more reasonable cause, Apple argues that it isn't illegal retaliation since they have reason to suspect Epic will breach contract, so it isn't entirely clear. But it is clear that free speech is highly relevant to this case and the courts will decide if you are allowed to retaliate for this kind of speech or not.

The point is that EU employment law (whether somebody can be fired upon saying things) isn't relevant to a dispute between two business entities that are not in an employer/employee relationship...