Remote Procedure Call is a design paradigm for synchronous call-and-response network communication. The Sun RPC protocol is an actual technology defined in RFC1057: http://www.ietf.org/rfc/rfc1057.txt
It's not insane, though not terribly relevant in the modern world. The only common technology still using it is NFS.
If you look at the original RPC work by Bruce Nelson [1], it's pretty clear that there's no strict definition of it. I think most would argue that SOAP would be included, which is still pretty common.
When Youtube refers to Vitess as being RPC-based, they are not referring to Sun RPC (callrpc), but rather to the generic design pattern of exposing service calls over the network. In particular, Vitess makes services callable [-] using either BSON or JSON serialisation over HTTP CONNECT calls.
