Brian,
The original 18th played straight up a steep hill toward the clubhouse. It was one of the most awkward holes I've ever seen.
The new home hole tacks across the same hillside, with the clubhouse right of the green rather than behind it as before. This 'fix' was possible, in part, with the addition of the new 17th you mention.
Liddy's 18th is undoubtedly much more comfortable than the original finish at the Dukes.