I think there's always been a blur with some of these vendors between domestic and CN. Product enroute to the US may sometimes be sold as domestic even though it's not on US soil. This "cush'' of items in transit allows the cash to keep flowing and new orders being created. This would explain the long lag times between "label created" and actual movement. Anyone with a USPS account can create a label to appease a buyer without having a package to send. I had a label created by QSC in early November that to this day shows no movement.
If overselling domestic supply is a strategy it works. I paid for my 1st QSC order only to be told it sold out and I could increase my order to CN MOQ for free shipping. Turned a $150 domestic order into a $300 CN and gave them a large window to deliver. I was happy with double the deal and in no hurry to get it but based on the fact my order was placed/paid/address confirmation email rcvd moments after the promo was posted I definitely felt like it was a bait and switch
I think all of my CN orders (QSC, SRY, AMO, +) have had a US origin. I assumed a large parcel gets drop shipped in the US where it's broken down and all those USPS labels get affixed. So maybe the USPS part of the process is after the product is already stateside (?)