Suzanne S. Barnhill shared this with us in
microsoft.public.word.docmanagement:

Different strokes for different folks. To you and me, pressing Insert
seems easier, but to some users, clearing the check box makes the
process clearer. The same thing can be accomplished by
double-clicking OVR on the status bar.

I never knew what "OVR" means in the status bar. Never too old to learn!

--
Amedee Van Gasse