Like the packaging shown in that Ebay link is incorrect for an AT&T variant. AT&T almost never uses OEM packaging, instead they use some weird gimpy branded boxes of their own. If it didn't come in a box like this, then it was a fraudulently repackaged and was not new:
https://i.imgur.com/n2dFAq2.jpg
Also the printed inserts should have AT&T branding on them, and will include AT&T-specific inserts. The flood of fraudulent LG V20s usually include generic international versions of the printed inserts. Watch for the IMEI label on the box being pasted over with another label, to hide the ID numbers of the device the box originally came with.
Just because its not new doesn't mean it might not work fine, it just means you'll likely never get warranty coverage; or if you do get LG to accept it once they examine in-house for repair you're probably boned.