People were advised all the time to avoid third party and order directly from the factory shop where possible (since even from Amazon it seems to have happened to receive HW with seed already in, I will look for link, but I don't promise results) and this may be a problem for your business.
Maybe you are talking about
this incident that involved a Ledger Nano S that was purchased from Amazon in the UK. The person who bought it, got a paper card already filled up with a 24-word seed. Not sure if the seed was also entered in the hardware wallet, but I am guessing it was.
I agree with what DdmrDdmr said in the OP. This can be a device that was tempered with by someone at Amazon, or it could be a hardware wallet that was bought by a different person altogether. It was that other person that set it up, wrote down the seed words, and then returned the device back to Amazon for whatever reason. The personnel who received it had no idea what they were doing, they just checked the contents quickly, noticed that everything seemed to be OK, and placed the package among the other ones waiting to be sold.