Mike, There have been reports and the subsequent incredulity by some.
My suspicions are that these changes were made to ensure Pebble's rotation for the open. At least that's their thinking. In the case of the third hole, it's obvious to anyone, (But RJ Harper and Arnie Palmer) that the added bunkers in the hillside, do NOT make the hole more difficult, which was their desire, but, in reality, easier. Hitting that green from that position in the rough was as hard a shot as one could muster. The added sand bunker has removed the need to be accurate on distance off the tee. Hitting the green from manicured sand adds spin to the ball removing the likely hood of going through the green which brings OB into play.
The 15th hole is an abomination.
The only decent change I can see is the removal of trees along the cove to the right side of the 6th hole.