IIRC it was one lower court case in Germany... That's so many asterisk attached as to be meaningless, even if that judgement isn't struck down or amended (unlikely), that still only applies to Germany (or was it one state within Germany?).
The way the EU works is that it mandates each sovereign country to implement the mandate into their national laws, so jurisprudence in Germany doesn't mean anything at all anywhere else.
Civil Law (used almost everywhere in the world outside the Commonwealth) still has Case Law, but it is held subordinate to legislation (itself usually built on top of Roman and Napoleonic law), whereas historically common law is built out of nothing but case law (because English kings had better things to do than concern themselves with the squabbles of peasants).
Still, when presented with a novel case that isn't specifically legislated for, judges in Civil Law countries can still make a ruling, and subsequent trials will have to take that ruling into acount.
How is that relevant? Just because some foreign entity has different laws doesn't mean you cannot have yours. We shouldn't always repeat us policy as gospel. Just look at their social policy nightmare.
To discern if an add blocker is in use you are processing information not essential to your service.
You could, eg. Not start the stream until the add is over if it wasn't blocked without violating this. In the end whether or not the user uses an add blocker is not relevant to your ability to stream a video.
Basically the stuff they need to detect whether ads are actually shown needs information of the device state that are generally not available according to Article 5(3) ePR.
It was some low effort attempt talking about "code that I do not like running on my PC" or something like that, words like "malware" were thrown around. Basically if detecting adblocks is illegal so should be any JavaScript code.