Mac is not an acronym.

It is only an abbreviation of macaroni.

Mac and Cheese would be redundant if it were an acronym.

Yeah, nobody would say the words of an acronym, like PIN number or ATM machine!

(you are correct)

There’s ATMs and there are ATM machines and you don’t want to get the two mixed up

Oh yeah the Access To Money machines that you see at sketchy convenience stores and whatnot usually have bizarrely high fees

Whereas Automated Teller Machines operated by established financial institutions are a little more trustworthy and reasonable

(I’m only a little bit joking)

Same feeling with “VIN Number” ._.
PIN is an acronym. ATM is an initialism. Please pedant properly.