Thomas, the pond wasn't even a pond until 1955. You can see in the 1941 aerial that it was originally a stream running all the way across the front of 15 from 17 fairway. By the time the pond was brought into existence in 1955, the trees right would have been very tight to the water's edge, if there was even an edge on the right side at all (I'm unable to confirm the pond's shape at that time, but looking for more evidence). I can't imagine many people would aim for a 5 yard wide sliver of land between trees and water to play a run-up shot, and those that did had two years before the bunker was installed.
The bailout on 15 has always been long and right. The bunker added some penalty to employing that strategy and forced players who bailed to choose between leaving themselves a sand shot or going well long off the rear downslope to leave a dicey approach back toward the water.