They likely won’t care, especially if you are returning it to immediately buy another iPhone and one that costs more. Just be polite, friendly and I’ve found that gets you far in Apple stores.
Thanks! Yeah, on the 2nd return I made here about a week ago, they didn't seem to care at all- the staff in the store just seemed to operate as if it was straight forward business, no concern as to why I am returning the phone. Maybe it helped that I was also picking up a new one at the same time in that instance.
As noted, yes I will be doing that as well this time if I do make that move, placing an order for the same phone (for in-store pickup) with higher level storage and returning the one I have, so again I suppose it will be apparent to them what's going on and they are ultimately getting more money out of me than what they got previously with the phone I'm returning.
And absolutely, polite and friendly is the name of the game in any retail situation- the staff doing this work deserve it, especially since the ones in the Apple store near me are all so friendly, too!