I point to things like DisneySea... not contractually obligated to reach that high and far. And as much as Disney won't enforce decorum on it's own guests or park operations.. do you really see them threatening OLC if they slide below some standard agreed to 30+ years ago? All MHO.. but I'd wager OLC's operational track record is based on their own pride and duty.. not fear of Disney legal hawks.
I can tell you that Disney does have a team of folks who go over there regularly and ostensibly make sure the OLC is following their legal responsibilities.
But I also agree that OLC's pride is likely far more of a factor in running those parks to such high standards, standards that Disney will never match anywhere.