Dave Meltzer from F4WOnline.com discussed why the WWE didn’t announce The Rock’s appearance beforehand on Wrestling Observer Radio, noting that while announcing him in advance would draw bigger ratings, Rock is more focused on the crowd reaction and surprising people in attendance as making WWE appearances is all for fun for him at this stage in his life.
It does hit way differently this way. So long as they aren't worried about the rating or needing to move extra tickets, I hope they continue doing the surprises.