I hear you on the "superstacking isn't an effect but a design". But I want to unpack/examine that idea as there are some potentially important technical points for recreating this and similar effects.
If we say the goal is the sound of "unison stack detune with stereo spread" then I'm aware of 4 potential ways of getting this or close to it:
use a synth or OSC designed to do "superstacking" (as Ronin suggested). Lots of VSTs do this (or very close to it): Serum, Sylenth, Zebra2, Icarus2, etc. Some Eurorack OSCs do this: Chainsaw and a few others. Some hardware does it (Waldorf Quantum and others). One can do a basic version of this with any multi-OSC setup; Moog Model-D with its 3 OSCs slightly detuned sounds great.
use an Animator like AJH Wave Swarm or Ladik L-011 Animator. Ladik's text says "Think of it as VCO extension – exact tone tuning ensures your VCO and Animator creates 8 phase-shifted and endlessly moving waveshapes summed to Animator´s output. Sounds like 9 slightly detuned VCOs together, sounds simply FAT (8 shifted waves + 1 original from input). Contains 8 phase shifters drived by 8 LFOs at 8 different frequencies (34 opamps total)." SO, as far as I can tell, the "animator" technique is like mult (of original) plus phase shift, plus LFOs modulating phase shift at very slow rates. The Ladik module has no controls, the AJH module has gain controls and 2 channels (which would allow for stereo / spread effect).
use delay-based effects (chorus and similar). While I love chorus and use it a lot, I do not find the chorused sound or controls equivalent to the "unison stack detune with stereo spread" sound or controls. It is close-ish, but often not close enough. The "artificial double tracking" VSTS like Melda MUnison and Waves Reel ADT I am less familiar with, but my understanding is those are also delay-based, and I don't recall those giving a sound like technique #1 above either.
use a combination of 2&3 as found in Kilohearts Ensemble. That's the only VST I know of that gives a software implementation including technique #2 above.
So Ronin, I don't really disagree with your point above. BUT I am trying to answer essentially the question: can techniques #2 and/or #4 above produce a sound similar to that of technique #1, e.g. similar to genuine superstacking? OR is there some other great solution I don't know about yet?
Practically, I'm wondering, if I do a sound design session on my rack and come up with this complex OSC chain I'm loving, is there a practical way for me to get the "unison stack detune with stereo spread" version of that sound? I would blow my brains out if I had to try to get a slightly detuned version of a complex OSC chain in 3+ parallel Eurorack voices (e.g. try to manually do technique #1 in Eurorack). I'm hoping something from techniques 2,3,4 above could work. AJH Wave Swarm is top of the consideration set currently.
Thanks for your ideas everyone!!