Yeah, it's confusing for us, too... we have a Prestige Pass for Knott's, and a Diamond Elite VIP membership for Six Flags. But as far as I can tell, if I just added on the CF parks at Six Flags, we wouldn't be getting the Prestige benefits at those legacy CF parks.
But we would if we get an All Parks Pass at Knotts. So we sort of have to go through Knotts, I guess.
Also kind of disappointed that it's appearing that the refillable mugs are not consolidated across all the parks. The CF one only seems to list CF parks (and costs extra), but the SF Membership one is still free (again, I think only for legacy memberships), but only works at SF parks. Was really looking forward to just having one mug for all the parks.