Le Marais is grandfathered in from the days when the OU didn’t require frum ownership. Now, if a place wants the OU, they need to have fru ownership.
I know friends who are mashgichim and they say the difference is like night and day between a frum owned business and a non frum owned business.
And for food service, kashrus is very expensive; the agency charges a lot for use of the name and their endorsement, while the mahsgiach temidi should be paid at least $20 an hour if bedikas tolaim is involved, in my opinion.