Who reviews new ELA and math textbooks?

Because most states adopted Common Core's standards, most school systems are investing in new textbooks for ELA and Math. And Education Week reporters are dutifully alerting their readers to reviews of these textbooks in ELA and math—mainly from a new organization called edreports.org. Reviews of math textbooks were reported in March 2015 and May 2016. An earlier blog dealt with the process itself.
Three major questions come to mind after I read Education Week's most recent article on review results, this one on edreports.org's review of English language arts textbooks. The most important one is: who are these so-called reviewers? Their understanding of secondary literature curricula leaves much to be desired.