[3.12] Fix inaccuracies in "Assorted Topics" section of "Defining Extension Types" tutorial (GH-104969) (#105850)

Fix inaccuracies in "Assorted Topics" section of "Defining Extension Types" tutorial (GH-104969)
(cherry picked from commit 0d0963737a0f4b7cadedfae7e8fd33ed18269289)

Co-authored-by: chgnrdv <52372310+chgnrdv@users.noreply.github.com>