The Fujisaki paper is basis for traceability in cryptonote ring signatures. The shadow token paper clearly describes a trusted ("special") setup to create an oracle as two hash functions. It is a deal breaker for true anonymity because it requires you to trust the person who set it up.
This is the exact same problem with all "zero coins". They require a trusted setup.
From my understanding... SDC's implementation is different from standard "zero coin" ZK attempts in that it utilises ZK in a way that the "setup" is similar to a dev who sets up or generates the genesis block.
In the SDC version of "ZK" it appears (to me at least, please correct if wrong) that SDC v2 only uses "ZK" to obfuscate the minted tokens exact origin whilst being able to prove their existance and therefore validate their redemption when passed on / spent.
It appears that the natural randomization of progressive use through multiple outputs (exchanging SDC for Tokens and vice versa) would signify that obtaining any kind of relative gain from knowing how it was "setup" if it was indeed relevant completely obsolete.
Still am trying to get to grips with this and would like to learn more but my conclusion so far is the "setup" you refer to and the way it's used in SDC's case is a bit like Satoshi "setting up" the Bitcoin genesis block.... It's relevant to a point of not being relevant once it's out because the coins on the blockchain don't lie and SDC coins will always be accounted for.
Not sure I understand how it would matter for this particular use?