No because just copy-pasting, or god forbid gEnErAtInG notes defeats the purpose of the note. Reading an existing note is secondary to having written it in the first place, because by writing it I can think about the topic and process different lines of thinking which may spawn other threads of interest or related issues.

Your example of git is one where I would particularly benefit because I could write about how git is structured or how a particular command works using the docs as reference and then find a difference between my understanding and the docs that I wouldn't have found by reading just the docs or just my notes. This isn't theoretical, it's happened to me every time I've started writing something on a topic.