Just return it ASAP there is the tendency of your Trezor has been compromised to avoid touching stories, that is one of my stand against using those hardwares, the possibility of stealing the phrase seed is very possible even from an insider in the factory, once those coins is stolen it gone forever, these are some of the risk associated with cryptos security and safety of coins against hackers.
You completely misunderstand the way seed is generated on a hardware wallet - although it is true that such a device can come in some cases with a pregenerated seed (used wallet/fake wallet), this does not mean that every user does not have to know that he must generate a seed before use. Workers in factories do not have much time to deal with such things, and after all, they are certainly under video surveillance all the time. There is a greater danger that something bad will happen to the device in the process of delivery, because then the delivery services and customs have the opportunity to open the package and modify the device or replace it with a fake one.
