Why would you type the wrong letter when you mean the other one? Authentication means proving what something says it is, authorization is allowing someone to do something.
The concepts are different so it's not like a dial you are turning to make a measurement, the terms are for different domains
While I also agree that authn or authz are perfectly clear,
> Why would you type the wrong letter when you mean the other one?
Really? Ignorance, laziness, rushing, fatigue, simple mistakes, etc.
What I think is worse is more letters doesn't save you. I've had some conversations where it has gone like 2–3 round trips before the other end realizes that "not" means not, and they mean … the other way.
The concepts are different so it's not like a dial you are turning to make a measurement, the terms are for different domains