DSS wings are sewn closed--no zipper. They aren't intended to be user-repairable. That's what we're talking about here.
Some are (Torus) some are not (LCD) As a practical matter nearly all wings, regardless of being zippered or sewn shut end up being returned for repair. The vast majority of divers lack the tools and specific knowledge of how a wing is assembled to be able to execute a repair, and most dive shops simply don't want to bother, or lack the tools and skills.
I used to sell bladders, and pretty soon stopped because far to many ended up botched, damaged, and the wing came back anyway. No manufacturer has an obligation to provide unlimited tech support to those attempting DIY repairs, and no manufacturer needs the headaches associated with selling a low margin repair part only to have it generate additional warranty claims.
Sorry if that offends some here who seem to believe there should be a constitutionally protected right to parts forever to anyone that demands them. Nearly every manufacturer is trying to maximize value for the customer, and losing money and devoting expensive staff time to a tiny fraction of DIY simply drives up the cost to the rest of the customer base.
Put another way, how can I know if Random Diver X is equipped and qualified to work on his own gear, or is he / she likely to start a complaint thread when they fail?