Guys, I had the same surgery as Tiger did. Had it in 1992. I think I know a little bit about how this type of injury goes as time goes by. What happened with Tiger today has a high probability of being one of two things.
1) His disc herniation left him in a state of health where the two vertebrae are close enough together that you can compress the spine enough to where they touch. This causes serious inflammation and pain, and that pain radiates and disables you.
2) The vertebrea are not touching at all. The issue isn't even structural. In this case what can be happening is that because Tiger had the prior injury he is now walking and maybe even standing differently. If he is the way I was he may be doing a ton of stretches to pull the verts as far apart as possible (think inversion therapy). Well, what can happen in this situation is you place new stresses on lower back muscles that have never been there before. Do it long enough and those muscles spasm. This is where the "it is in a different spot" comes to mind. Once the muscles spasm it feels like "its the entire lower back".
My bet is that it is this latter scenario in play. The good news is that this is not permanent in and of itself, and furthermore can be fixed in a few days with site injections. The bad news, if this has indeed occurred, it is a condition that tends to re occur every so often. You tend to end up looking just as Tiger looked today, and then a week or two later you are fine when everything calms down. Been there, done that, for 20 years.
Or 3) he just tweaked it like golfers do from time to time.