The advantage that the EU has in this situation is that it's better able to "negotiate" as a bloc of 450M people, than (to use the upstream example) eg. Malta, with 440,000 people.

If individual countries want to require a local content quota, Netflix/Amazon/etc will simply cut them off. When it's a massive market, that's vastly less likely.

Giving individual countries an opt-out from the EU-wide rules just provides an opportunity to divide and conquer.

Australia has similar content quotas for broadcast television, but hasn't tried to apply them to streaming services yet. Of course, for 25M people, our leverage is substantially less.