Really wonderful to come across this article, Sofia and Ray. I agree completely. I appreciate that you identify the nuances of making contributing easy as possible and consistent. Also, valuing documentation contributions as equal to code.
I suggest adding that sponsors critique the underlying platform and information design of the documentation from the perspective of personas. That is an unlikely process for typical contributors to do, but possibly very eye-opening.
Sponsors need to be clear eyed about what contributors are equipped to do and what gaps are left.