No, the reasoning in Melee was entirely that Fox would always win regardless of the match up. He wouldn't win just because of the walk off, but it was the walk off in combination with the low ceiling, meaning even if you play on the left side you'll still be KO'd around 60-70% (depends if your on the hill, I believe the highest perfect is around 80%) from drillshine upsmash, which if you remember anything from Melee, is unblockable for most characters (at least if the drill lands). Throw in Fox laser camping the right side and your only out being edge stalling the left side and you have tons of other problems. In Brawl, there are far more projectiles that are viable, and D3 doesn't have a quick ranged projectile, therefor a D3 can't camp right side against, say, Pit, and expect to still be dealing damage.