I also cannot discern what the "math-review" tag is intended to cover.
While those three tags (proof-verification, reference-request, and soft-question) mentioned by @AloizioMacedo may be broad (tags do generally have more breadth than individual Questions, by their nature), I think I have a pretty good handle on their "specific" meaning and application.
Tag "math-review" suggests a variety of things to me (such as the published Mathematical Reviews, often used as a proxy for publications that may be inaccessible) that are not reflected in the use or wiki summary of the tag. So it is unclear to me whether there is a valid need that this tag tried to address, but clarity is needed to make a tag useful.
Or as Aloizio comments below, it might be worthwhile as a tag if not for the bad tag name and a bad tag wiki!