It's a computer asking for an action talking to a computer asking for an action.
Call them whatever you want, the concept is extremely simple and pretending it's anything more complicated is obfuscating the underlying simplicity of the intent of the programmer. i.e. I want the other computer to do something or the other computer to send this computer some information.
The intent is simple, but there are many ways to express that intent. Some of them work well when there are two components sitting right next to each other in memory on one machine; others work well for an unknown number of components interacting with each other over a slow, unreliable network.
Even if RPC is a fundamentally, unambiguously simpler way to express that intent (and I think that's arguable), it does not meet the same technical requirements that REST does.
It's a computer asking for an action talking to a computer asking for an action.
Call them whatever you want, the concept is extremely simple and pretending it's anything more complicated is obfuscating the underlying simplicity of the intent of the programmer. i.e. I want the other computer to do something or the other computer to send this computer some information.