a) There is nothing that prevents YouTube, Twitch, or Twitter from using algorithms solely to alert a human reviewer (except personnel shortage, which can be remedied by hiring more personnel). In any case, shortcomings in algorithms are reasons for better algorithms, not excuses for spreading illegal content.

b) With statements about a person having been found illegal in court, the victim has a right under German law to be protected against any further spread of such statements. How Twitter or anyone else implements that is not the concern of the court any more than "I didn't see the speed limit sign" is a valid excuse for speeding.