Well, I guess it depends what you mean by "overbunkered".
There are certainly more bunkers than we needed to define the lines of play. I don't know how many bunkers I dug on holes to start with, but Mr. Nicklaus added quite a few and didn't take very many out, and Mr. Pascucci might have suggested a couple as well. [For one, there is a bunker to the left of the 6th fairway that mysteriously appeared a couple of years ago while I was away.]
But, it should also be considered that Sebonack consists of just four landscape elements -- trees that had to be preserved, native grasses that had to be restored and tend to be very thick, short grass, and open sand. From that perspective, I would contend that Sebonack already has plenty of trees, plenty of native grasses, and plenty of short grass, so I don't mind that there is as much sand as there is.
Two of the bunkers added by Mr. Nicklaus were at the par-5 9th [which is the 8th hole for the tournament this week]. The fairway bunker in the left-center was an impossible carry for any of the women I watched from the tee as marked [they may move it up on the weekend], but the little bunker to the left front of the green did catch a couple of second shots, and caused the longer hitters to re-think how they wanted to play the hole. I always thought the hole would be fine without the left-center fairway bunker, because even if it wasn't there, you would have landed into a crowned upslope and had a heck of a stance for your second shot ... but I got out-voted on that one.
As for the third hole, depicted above, being way out to the right is only the best angle of attack to front hole locations. Where the flag is on the green, I'd love to be as far left as I could be on the tee shot. I have even played down that alley to the left of the bunkers, but I doubt you'll see anyone do that this week, on purpose at least.