How do you reconcile your points 4 and 1? Say I want to answer someone's question on Slack. First I have to change the docs, but doing so would require a whole PR, alongside approval, which may take one or multiple days.
This has the added benefit that you can have some back and forth to get to the root of the question before documenting it.
The key thing is that you have to make sure to actually do the step after (transfer to docs), even if it's a quick copy-paste with minimal editing.