This same situation also happens if you have to file an actual warranty claim (instead of an insurance claim) and you get sent a replacement device from the manufacture (e.g. LG/Samsung/etc) instead of the carrier (Tmobile/Att) I have like 5 manufacture warranty replacement devices that are carrier branded with clean imei but the carrier claims they aren't carrier branded phones even tho they are loaded with said carrier bloatware, boot splash screens and carrier branded boxes. So if you ever see a phone on eBay/swappa that is a near mint refurbished/warranty replacement avoid it off youre trying to get it unlocked