I guess it says something about OAuth when you implement it "at scale" and still have multiple misconceptions (all very common though).
Most importantly, OAuth is an authorization framework, OIDC is an authentication extension built on top.
Refresh tokens are part of authorization, not authentication.
HTTP header is Authorization: Bearer..., not Authentication.
There's no such thing as "HMAC encryption", it's a message authentication code. RSA in OAuth is also typically used for signing, not encryption. Not much "encryption" encryption going on in OAuth overall TBH.
Nonce and client IDs are not "salts", but ok that's nitpicking :)
Baby steps my guy, baby steps. Yes, I don’t even mention OIDC, but I think the way I explained it was the middle schoolers version we all can understand (even if there are some minor mistakes in nomenclature).
The point I was trying to make at 2am is that it’s not scary or super advanced stuff and that you can get away with OAuth-like (as so many do). But yes, OAuth is authorization, OIDC is authentication. The refresh token is an authorization but it makes sense to people who have never done it to think of it as a “post-login marker”.