I re-write rules for myself for games where I need a better teaching "script". For example, the Keyper rulebook was terrible, but the rules themselves were not. I wrote myself a summary so I could re-teach the game if needed.
Yes! Anything I'm serious about learning, I (re)write the documentation as I go. Haven't tried this with board games yet, but it actually sounds kind of fun.
For me, at least, there is no rulebook or textbook or docs page that is so great that I can learn about something just by reading about it. Unless I can mess with it (even just by writing my own text about it), I will never internalize it.
https://boardgamegeek.com/filepage/269820/keyper-quick-rules...
https://boardgamegeek.com/boardgame/212516/keyper
And Smartphone, Inc, because the rulebook was bad for looking things up quickly:
https://boardgamegeek.com/thread/2979178/some-rules-notes-i-...