Well this is going downhill.
I think "Melee vs. Brawl debate" is like the Godwin of this forum. Any convo that goes on long enough will eventually be about that.
In any case, a few pros looking at a game for a single day, or even a few days, is nowhere near as good as every pro looking at a game for well over a year. You just aren't going to have the same quality of analysis. I don't really care what you say or how sure you sound when you're saying it, because the math says you're wrong. I'm sure the current tier lists are made as good as they could be, but some of the people making these tier lists admit that they're incomplete just because they haven't been able to play every character.
Don't get me wrong. I know it's perfectly possible to memorize a moveset in a few minutes via button checking, because I can also (sorta) do that. I also know it's not impossible to test things like priority or knockback angle. From there, it's almost trivial to come up with meaningful combos. I know all of this both because I can do them and I've seen other people do them. It's not hard to believe that the pros had a solid, basic understanding of the build they were playing.
However, it is a fact that the damage/knockback model of the game wasn't even finished for E3. This isn't some minor damage tweak. It's a basic, fundamental part of the way the game is played. If Brawl or Melee suddenly had different formulas to model knockback, don't you think that would change the game? Just a tad? Because I think it could actually change it quite a lot, depending upon how big the changes were. Maybe air games would be a lot more important, or maybe the ground game would become king, or maybe recoveries become less important because guaranteed KOs are just too easy, or maybe the game takes a longer time than it should to drop stocks because KOs are too hard. All of these things would have an impact on how both offense and defense are handled.
Also, we have competitive players doing analysis of the Best Buy demos. I don't see a lot of them saying that this game is "Brawl 2.0". What I actually see is them saying that the game is very well balanced aside from Zelda, that they like the way the game is going (as far as they can tell), and that some basic defensive options (like Shields) have been gimped. How are gimped defensive options going to lead to campy gameplay? People who play to win are only going to rely upon camping if it gives them an actual advantage. If it's a disadvantage, no one is going to seriously do it. If Shieldbreaker moves become part of the Smash U meta and they end up being common to a lot of characters (not just Marth and Bowser), then that's a pretty significant change that the pros haven't had time to look into yet, and you can be sure that it's going to nerf defensive play in a significant way.
The metagame of both Brawl and Melee has changed significantly over the years. Yes, Meta Knight rose to the top quickly and then rose even higher, but it's also true that Sonic went from low tier to mid tier, and one of the big differences was because people found a completely different way to play him. Pros don't know everything right away. They can't. There's no way to have god-like knowledge of a game from screenshots and two outdated builds. Even if a well-trained finely honed mind absorbs all it can possibly absorb from the available information, it's not going to be able to absorb information that simply isn't there. It may seem that some pro players have psychic powers, but in reality they just have good pattern recognition and not true omniscience.
For example, do you have any idea how the Lucina vs. Marth matchup is going to go? Probably not. Sure you can give it your best guess, but since no one outside of Nintendo has played Lucina then no one outside of Nintendo really knows how it'll go. Maybe Marth's tipper mechanic doesn't help him that much, because Lucina can just get inside his zone and still deal optimal damage while Marth gets weak non-tipper damage, and even when Marth is at his idea range Lucina is still at her ideal range because every point of her sword is her "ideal range". Or maybe Marth has the upper hand because he always has good options for getting into tipper range and there's nothing Lucina can do about it. There are a lot of ways this match can go depending upon how the dev team assigns the numbers, and we simply don't have those numbers.
I'll put stock in what the actual pros say when they feel confident enough to not feel the need to put massive "we don't have a finished game, we didn't get to play all the characters, and everything is subject to change" disclaimers before everything they say. Until then, I'm gonna recognize the same limitations that they also recognize.