gh-109510: Clearly explain "Which Docstrings Are Examined" (#109696)

Co-authored-by: Mariatta <Mariatta@users.noreply.github.com>
Co-authored-by: Jacob Coffee <jacob@z7x.org>
Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>
Co-authored-by: C.A.M. Gerlach <CAM.Gerlach@Gerlach.CAM>