Is there an official page from YouTube that lists banned categories? Even YouTube's public policy page [1] doesn't mention anything about educational hacking videos.
It's there somewhere, but it doesn't say "educational hacking videos". It says "hacking and spam/phishing".
It's just a rephrasing of their existing policy. It's the same idea of why they don't let you show videos advocating building bombs and using them in terrorist attacks. The videos that are banned are based on people trying to use these techniques to commit crimes. Not banning "hacking" in general.
[1] https://www.youtube.com/about/policies/#community-guidelines