I would really be interested to know what they would do with the returned powder. There are so many crazy and dangerous people out there that they really couldn't know if the powder was tampered with. The risk of reselling powder from an unknown source is way too high.
A different powder issue:
A LGS in PA that I often bought powder from started selling powder in mislabeled powder containers and some powder was being sold in Chinese soup containers. When I asked about the origin of the powder, they told me that they get 8lb containers when 1lb containers are not available, and they break it down and put it in whatever they got. They slap a piece of paper on the front with the powder name.
I would never buy one of those containers. I don't suspect foul play but if one of their employees made an innocent mistake, the buyer would pay the consequences. I want my powder sealed in the original container and received from a reliable source.
BTW - my comments are NOT directed at the OP who ended up with the 8lb jug with a return request. They are just my thoughts on the topic.