This is what I was told when I used this program on the Oneplus Watch 2, I messaged them that I didn't get any trade in shipping label, and they said the recycler information is in the fine print to just contact them to send it in, or don't, it really didn't matter I wouldn't be charged back either way.
It wasn't a "flaw" or loophole, if anything it was just laziness, but basically the trade in any device, any condition just instructed you to recycle the device and gave you their recycler companies information in a small footnote at the bottom of the screen that most people never paid attention to. Nothing has changed now, except that you will now get an email from that company as well, but you still won't get charged for it if you don't send it in.
OnePlus's alternative trade-in program provides a $100 discount on new purchases if buyers trade-in an old device regardless of its condition. Now, it's fixing a flaw in the program.