Confusion about AT&T unlock instructions
I am preparing to sell an off-contract AT&T iPhone SE (2006). I reset it and then afterwards I decided to request that AT&T unlock the phone so I would be able to sell it as an unlocked phone to a wider pool of potential buyers. AT&T approved the unlock request. The email from AT&T says "we approved your unlock request. Use these instructions to unlock your device. *Using a non-AT&T SIM*: remove your SIM card and insert the new SIM card. *Using an AT&T SIM*: backup and erase the iPhone and restore from backup. *Contact apple support if you have additional questions*".
I do have this additional question: I am selling the phone so I don't know if my future buyer will want to use the phone on AT&T or not. I think I want to remove and dispose of the old AT&T SIM card and just sell it that way, noting that the phone does not come with a SIM card and is unlocked. Is that fair to say--even though AT&T's unlock instructions suggest that the unlocking is not complete until the new SIM is inserted.
iPhone 6, iOS 12