Some characters have "quintessential" habits I suppose.
In Brawl, Marth was similar in terms of "the jump", as was how he was going to land (single timing for power shielding his fair). Having such specific play patterns with certain timings comes back to haunt players breaking through mid level (and will be what "better" players will eventually start to learn as part of how to deal with a match up and be able to produce ugly things).
So with Marth it was important to vary timings, alternate with neutral air, or fast fall land instead. Or dtilt/dancing blade/shield more and punish people trying to punish a jump you didn't make.
In Smash 4/ZSS' case, they develop overtime. Seemingly optimal game plans that will basically never go punished unless people are thinking 2-3 steps ahead (i.e. bridging reaction: "react that they're landing with nair" with anticipation [dash forward here and expect them to dash/roll away]).
When you look at how ZSS can mix it up with not dashing away is pretty risky actually, jab, up tilt or ftilt are fast but can be punished shielded close pretty hard, so in reality dashing away is still one of the best choices to take, but you need to be ready for the opponent knowing that's your best choice.
I would say the "three" habits are
1. Bad jumping: the predisposition to always think you need to be in the air to be effective (must nair, bair, etc ASAPASAP), when if an opponent is on top of you this is a terrible terrible choice. Similar to the preceding paragraph, if you're going to make this "choice" you need to be ready for them trying to punish it; at this time it's air dodge, jump, down-b, yolo aerial. As a point of interest, down-b started early from a jump can be acted out of before touching the ground. But realistically instead of thinking "jump anyway, air dodge, then try to hit them coz they'll get baited", you should be thinking "shield... roll away, jab, ftilt, ANYTHING ELSE".
2. Grabs: "play passive until the grab comes and react to it with a forward roll and kill them". Harsh reality.
3. Attack -> Defense pattern. I mean, it's probably not fair to call it a ZSS only habit, it definitely wouldn't be. This is such a well understood smash bros habit (at least from the brawl meta) that against any competent Brawl player if they realise this is what you're doing, they're likely going to bop you. Basically you're landing with an aerial, something that should be safe and generally cannot be challenged by most of the cast, then what do you do? Dash or roll away. You're at a frame disadvantage from the aerial no matter what, but not enough for a guaranteed punish, but if they take the "hard escape" read (it's actually quite reactable once you get used to it) they're very likely going to be ahead of you on your action with enough time to punish, and they're going to do so
without fear because a lot of players don't ever not do this; when a few attacks, maybe a yolo smash, will scare the living daylights out of them into not always going for this. This one binary difference in game play choices forces a major upgrade of necessary respect for an opponent at
all levels.
Anyway, why I feel I know this well is because I'm 1 of 2 ZSS in my region and I've never lost to them in tournament. I've told them this after every set too. It's a hard thing to shift, and it's easy to fall back into.
Someone gave me the same advice at some point in Brawl too and I shortly after never lost to that person in tournament again. I still would probably do something passive/defensive, I just would be paying attention to them trying to punish it and win out a lot more often
[in Marth's case it was bull **** because of 1 frame invincibility up-b lol]