I think the uniforms or lack thereof are not helpful as evidence. Sloan on DS9 only wore a SF uniform in his first appearance, and it was as subterfuge. All the rest of his appearances, he wore that leather number, as did most of the other S31 folks we saw.
Well, none of them had starfleet uniforms. But, section 31 is part of the original starfleet charter. So, yes and no?