ZSS DOES have a guaranteed regrab on Wario, it's just hard cause you have to be nearly frame perfect and buffering it causes the grab to come out too early, and if you miss then you get uaired/fsmashed/ftilted/farted on.
The ZSS air release CG definitely matters in the MK MU, cause the pummels she gets out of it boosts her kill power in the MU quite a bit. eg normally uair is stale so it won't kill til about 150 or 160, but getting a grab near, say, one edge of FD, you can get in 9 or close to 9 pummels + damage from a throw (this is at least 20%) and now all your other moves are fresh. Oh and surprise surprise, fresh uair kills MK at 138% on FD and it happens to be guaranteed out of air release, how convenient.
Also the ability to refresh your moves so easily as a result of the CG means that ZSS doesn't really have to worry about bair getting stale in this MU.
And then there's also the little things like taking advantage of walkoffs (Delfino now a riskier CP for MK), getting an CG across the moving platform on SV --> dsmash (very gimmicky I know), and air release into walls --> dsmash.
All in all it doesn't matter much cause ZSS' grab is still butt so it's hard to grab in the first place, but each grab makes quite a difference thanks to the ARCG