It has zero performance advantages If you had to go the TLS route and wanted better perf, then it'd make more sense to build a new, dead simple, framing protoc

It has zero performance advantages If you had to go the TLS route and wanted better perf, then it'd make more sense to build a new, dead simple, framing protocol that actually specified working pipelining and eliminated HOL blocking by allowing out-of-order responses. They're just using HTTP because HTTP(S) defaults to port 443 and it'll go through more firewalls, and I guess their thinking here is to (just add more complexity) and move to HTTP/2