Liberal Richard Holbrooke has this to say about this topic
“The idea of giving U.N. ambassadors “Cabinet rank” is a “bad tradition,” Holbrooke wrote back in 1982, that “against reason or good politics has allowed the [ambassador] to become a sort of second secretary of state.” In an op-ed piece for one of his local papers when then-Secretary of State Alexander M. Haig Jr. and then-U.N. Ambassador Jeane J. Kirkpatrick were feuding, Holbrooke said such friction was inevitable no matter who occupied the offices. “Cabinet rank” has been “a valuable political goodie presidents have handed out to people whom they do not quite want to appoint Secretary of State,” Holbrooke wrote.
Do you have a link for the Holbrooke info?