Steve,
The bunker has an interesting history and wasn't included in the original design.
Change doesn't happen rapidly at PV and the bunker is legendary, hence, I don't know that substantive design changes would be made as their budget seems capable of handling maintainance issues caused by what you refer to as an inherent flaw in the design.
I'm probably part of a shrinking number who played the bunker when the putting surface fed balls directly into the bunker.
In the early 1960's, I first played the course with two good Pros and a very good friend. My dad had been playing it for decades and had told me stories, interesting stories and horror stories about the experiences of people he played with at PV.
When I came to the 10th tee, I didn't get an uncomfortable feeling, certainly not the shock to my system that occured when I arrived at the back of the 5th tee.
Anyhow, I hit my approach about 15 feet from the pin which was cut pretty much front slightly right of center.
But, as I walked past the D.A., my curiosity got the best of me.
So, I threw a ball into it and descended.
I was struck by the ice cream cone nature of the bunker and the thought that if I didn't get the ball out on my first shot that there was a good chance that it would return to the bottom of the cone and lodge in one of my footprints.
I took a normal swing, but, the ball caught the top of the bunker and came back to rest in the bunker, but, miraculously, not in a footprint.
I then took a bigger swing, hit a terrific shot up onto the green, then to my horror, watched as the ball slowly rolled back toward the bunker, then down and back into the bunker.
Now I was pissed.
So the caddy says, "I'll bet you $ 5 that you can't get on"
I accept his bet and widen my stance to the degree possible, take a mighty swing and "viola", the ball comes out about 10 feet from the hole.
In those days unaccompanied guests were permitted, so, the other amateur in my group, a good golfer, who had never played PV, has the bunker restored and drops a ball into it. He takes one, two, three, four, five shots and it's getting worse and worse since the narrow bottom of the bunker is basically deep footprints. Finally, after about a dozen blows, one of the Pros, kidding him, says, "Why don't you try going out backwards, because we don't have all day to spend here watching you dig to China". So, he turns around and hits it out backwards and says that he wished that he had thought of that on his first attempt.
I know the bunker always had drainage/washout issues, but, I wonder, given the manpower and budget, if the deflection lip wasn't added to speed up play rather than to improve drainage ?