I watched this video yesterday too and it inspired me to write an article (not the longest article, its mainly to provide download links for those NES games): Nintendo Family BASIC Type-in Programs Collection (homebrew roms for NES)

The video itself is as you say, surprisingly interesting. But to be honest, I expected that. This channel has often interesting content like this. BTW Masahiro Sakurai, the creator of Kirby and game designer of Smash Bros., had posted a video about this system too. Its very interesting watch as well: Family BASIC [Programming & Tech] by Masahiro Sakurai on Creating Games