Working for a company much smaller than FAANG, I've seen issues with REST. However, the waterfall problem was a small issue compared with problems with bandwidt

Working for a company much smaller than FAANG, I've seen issues with REST. However, the waterfall problem was a small issue compared with problems with bandwidth and server-side compute when you are processing and returning more data than is actually needed. That isn't to say that graphql is a magic bullet for those problems, but the issues with REST can show up far before you get to FAANG scale.