"But since when and why is a tighter pattern better just because it is smaller?"
Gerhard, I know it is pointless to argue with you, but it is kind of fun. To answer your question:
Since always.
This seems to be the exact same situation as with the bear defense thread, your argument is only valid if the person firing the gun misses. Yes, a wider spread is indeed better than a narrow one if I miss the target by just a hair, but if my point of aim is on target then the narrow one is considerably better. You seem to believe that nobody in the entire world is capable of hitting a target with a shotgun and so should plan to miss their intended point of aim and then rely on wide shot spread to hit their target for them. That is a complete failure of logic.
Benefits of a tight pattern with buckshot:
1.) Less chance of shot missing the target and hitting someone/something else that you would prefer not to be hit.
2.) If you hit the area you are aiming for on the target then you will get far more shot in that target area and do more damage.
3.) You can fire from further away and hit the target with more of the shot. At 35 yards without flight control you are lucky to get 3 pellets of 9 to hit a man-sized target. With flight control you would be unlucky to get less than 6 pellets of 9 to hit the target.
I would think you would be ALL about this idea given your firm belief that 000 magnum buckshot is better for Alaskan bear defense than 600 grain magnum slugs. One of the stronger arguments against 000 is that you can't hit the bear reliably at more than 25 yards, and if you wait until it is at a more reliable range like 15 yards you will only get one shot no matter what instead of having a chance for two or more like you would with slugs. If they ever released a 000 magnum with flight control that would at least make that point against your argument a little less strong.
4.) Third post, first photo:
http://www.shotgunworld.com/bbs/viewtopic.php?f=7&t=257470&start=40
7 yards is home defense range. If you put 15 pellets of #1 with 14-18" gelatin penetration capabilities in to that small an area on someone whatever part of their body you hit WILL be destroyed. It will be destroyed in a way that only extremely heavy revolver or rifle rounds like .454 casull or .45-70 can replicate. The difference is those rounds, even in JHP form, are guaranteed to overpenetrate any human they hit and carry on a considerable distance beyond them where they may kill or injure someone else. So it basically wins on every level: It creates a larger single entrance wound than any handgun or rifle round. It spreads out after doing so to create a wider wound inside the body with more likelyhood of hitting vital organs or the CNS than any handgun round. It penetrates deeper than all but the strongest handgun rounds yet not so deep that it is all that likely to injure someone behind the target. Non-flight control does NOT do all this because even at 7 yards it creates multiple smaller entrance wounds instead, which means slower bleedout.
The one other advantage I see it as having is the reduced recoil. I personally have my HD shotgun loaded with five 3" #1 buckshot shells. Being magnums their is a ton of recoil and followup shots will be slower than I would strictly prefer. If I can get 99% of the stopping power of my magnum shells with half the recoil, that is a win-win in my book.
Sorry, but there is a very good argument for why this is highly effective home defense ammo, and superior for that purpose to regular buckshot.