The key word is "satisfactorily". Robert Harris would barely stoop to using a projection print at all. His standards are a bit high, and I think the statement reflects the fact that film preservationists usually have a lot of other resources available to them that have fewer problems than a tech IB would. If you had the OCN, why on earth would you bother to use the tech IB?

Nevertheless, it's interesting that he says it's only good for a color reference and that's, in fact, what it's being used for as far as most people are concerned.