It's all permisionless. If Tether or anyone wants to create a custodial fiat-backed SMT, they can certainly do so. My comment was more that it wouldn't be a direct substitute for SBD, but could be an alternative. Just as we have no say over who creates an SMT we also have no say over who uses them, so if that's what people want, and there is a willing provider, they'll certainly have it.