I see where you come from, but I think we have more positive than negative. The paragraph in question is about a trend that the author supports, as we see at the beginning of the paragraph, and in the opening line of the final paragraph. The author seems to be generally favorable towards the study, but notes that it is missing one element they like. This is a qualifier, but it does not seem to outweigh the positives. Moreover, I dont think we have ambivalence, since the author seems to still be noting this as a positive trend, although this author missed one element, and nothing about this indicated unease.
