Thanks for the question. I wouldn't really say there's a single sentence that we can point to that tells us the author's attitude is one of implicit endorsement. Rather, it's little hints and clues throughout the passage that help us come to this conclusion. In the first sentence, for example, the author describes Olsen's analysis as "careful," and the rest of the passage uncritically presents Olsen's arguments. Thus, though the author doesn't explicitly agree with Olsen's arguments, there does seem to be a kind of implicit endorsement in the passage. Hope this helps!