Wayne,
In the run up era, bunkers in front of the greens where the approach shot might land made some sense. What about that back string bunkers a good 10-15 yards behind the green, over some mounds that would contain shots, etc.? I can only imagine that they would guard a back pin position if it were all green. Not many folks, then or now go that far over the green to justify a bunker.
I figured all Biaritz were originally all green and then shortened. My first inclination is that since you provided it, you are looking at a base sheet of Flynn's reconstruction of Shinny, rather than a plan of how the green was originally built. If that is an original CBM drawing, then I guess some of them started out with fw in front, not unlike the GCGC green.
The short hole comparison I made is probably a stretch. I wonder in those rougher cut days how those ridges played. It would seem green surface would be better outside them to allow a putt. If a comparitively rough collar, the option of putting would be gone, I think, leaving a pitch over a mound, but then the mound on the other side would keep the shot in if it was a little long.
I figured it got bulldozed for maintenance reasons. But could it be that golfers of long ago just didn't like how easy it made the recovery? Tom N seemingly (I could be wrong) feels that RTJ forced it on them, but like Pat Mucci says, the club really controls it. Its more likely that they called him in specifically to modernize what had become viewed as a bad hole. And, that it MIGHT still be one conceptually for score based players, but for architecture buffs, worthy of recall, for historical purposes or to restore some of the original, early Amercian quirk that was too successfully bulldozed out of existence.