The last example is a bit sloppy. It is not correct to include the phrase "is wrong" in the last example as a negative referential just because it negates the former statement. There is a hidden or implied referential in the sentence ("But he is wrong about that.") where "that" is the referential, and it is not a negative referential. The fact that the content of the predicate is such that the author is negating the previous sentence does not make that predicate referential; instead, the referential is inferred.

This becomes clearer if you remove the first referential: "One prominent biologist, Dr. H, hypothesized that the colors function as camouflage. But Dr. H is wrong." There are no words in these sentences serving grammatically as a referential, although you can imply from context that the thing he is wrong about is the hypothesis.