iPhone 18 promotion question

My wife is considering upgrading to the iPhone 18 Pro.

She is currently on the Pro plan already, but she still has 3 months left of a $15 off per month sign up bonus from a couple of years ago.

I know the device credit promotion doesn’t stack with sign up specials, but will she still be able to take advantage of the device credits? Will they be able to start once her signup bonus is over?

Just want to make sure she won’t not get the $480 worth of credits just because she has a few months left of a sign up bonus.