what went into the meta analysis and why? What data might be missing from the meta review and why? Is only including double blind randomized controlled trials the best research method to answer the specific question being addressed? Was everything included together actually comparable?

The critiques / rebuttals to the masking review typcially ask these questions. This review almost falls apart after considering the answers.

If there's not enough information to form a solid conclusion, maybe they have no business analyzing it until there is. At the very least, if they're going to include partially unrelated studies, then reflect that in the title / opening statement. Don't say the analysis is of apples, then analyze fruit in general.