Do you happen to know the stamping date on the inner panel of that door? Come to think of it I saw a 68 door out in the trailer the other day. Guess I could check that one also
Looks something Ford thought of putting into production but never did. Likely there was another page to replace the page that ended up in the available copies of the Assembly manual the next day or week - as soon as they changed their mind. Pages came from numerous versions printed through out the year to make one good copy.
Just one of a number of details where the manuals don't match production exactly