Alright, so the fact that Zelda doesn't show up directly on the list of characters changed in 1.0 has apparently led to some misinformation. Allow me to explain why exactly it is that the game version can and will directly contribute to either winning or losing a match. In 1.0, if a move deals less than 1% damage it has no hitlag, meaning SDI is impossible to perform. Numerous multi-hit moves whose individual hits deal less than 1% by themselves, such as Young Link/Samus's up-b attacks and Zelda's forward/up smashes, were clearly designed around this mechanic being in place. They start with a bunch of little hits which link into a more powerful one.
In 1.2, a change was made allowing moves that are supposed to have hitlag normally to continue to have it even if they stale to less than 1%. However, in doing this, they screwed up and made it so that ALL hitboxes that do less than 1% were affected, including the ones in these multi-hit attacks. This basically means that an opponent can get hit by one of these moves, and SDI on the hitlag frames of the little hits in order to avoid the final hit entirely. The end result is getting hit by something like a fully charged Zelda f-smash and taking only 1-2% with no knockback whatsoever.
But that's not where it ends. Zelda's up-smash out of shield is, by far, her OoS option with the best frame data. In many shield pressure situations in fact, it's her only option fast enough to combat certain things, such as Falco dair-shines. With the added 1.2 hitlag on Zelda's up-smash, not only does SDI allow the opponent to avoid taking any damage or knockback from it, but they can SDI down back into the ground, ending up standing below the hitboxes being created above Zelda's head. Zelda will be stuck waving her arms up in the air while the opponent can do whatever they want against a helpless opponent, whether it be a Falco down-tilt or a Fox up-smash. It completely destroys any use the move has against an opponent who knows what they're doing. The difference is that of having a usable OoS option and not having one. It absolutely plays a huge factor in the ultimate outcome of the match. If that doesn't amount to "unintended consequences to poor game design" I don't know what does.