Thanks for the reply.

Actually, I ended up finding the answer to my question (“why doesn’t every assembly tutorial cover calling conventions on like, page 2?”), and it was because I was coming at this topic from a C perspective.

https://stackoverflow.com/a/17309038

“ If you're writing in assembly language, you can do whatever you want. It's only when you want to interact with some external code (maybe a library, maybe a system call) that you need to obey the calling convention.”