Why the political correctness? If you feel that ST types should be included in a discussion of rationalism/objectivity, explain why rather than just complaining that they aren't, please?
They were specifically trying to figure out which NT's were most objective. (And they weren't even sure if they mean objective, logical, or rational, so that was an issue as well.) I don't think anyone would argue that in many (if not most) situations, an S can be more objective than any N because they look at exactly what they see rather than inferring a pattern, and have slightley fewer cognitive filters applied to their sensory process (with the possible exception of memory). However, in some situations an S could be too predisposed to focus on past experiences or how things appear on the surface rather than looking "beyond" the surface to see that things are different than they seem.
ST objectivity -- Sees things as they are, doesn't try to fit them into anything, doesn't try to form connections from what it sees, reports it accurately.
NT objectivity -- Looks directly at patterns/ideas as they are, is better at aligning things with the idea in an objective manner, without allowing the exact nature of it to interfere with the understanding of its relationship to the idea.