This is an interesting puzzle. I can't find any actual details via Google, so until someone finds something authoritative here are my thoughts:
First, we need to remember that the Kindle being pre-configured is the default flow, the device being shipped in gift mode without being linked is an exception. This means certainly nobody is opening boxes, setting up the device, and re-packaging them. The pre-configuration is happening domestically after the device has been received by Amazon from overseas manufacturing, since the turnaround is too quick for ocean shipping.
My first idea is that Kindles are shipped in bulk from manufacturing and are packaged for shipping in the destination country, and the pre-configuration happens at that time. This could make sense if Amazon wants to have localized packaging materials, but seems like it would be too much work happening at the destination country.
My second idea is that the Kindles are shipped pre-packaged to the warehouse, but something triggers them to wake up in the box and download configuration information before shipment to the customer. On the simplistic level, booting up once or twice a day at a certain time to check for a known Amazon Warehouse WiFi network with saved credentials, if present connecting and downloading a configuration package with your account cookies. Or having some low-power chip that is triggered by a particular signal on the shipping line, or geo-gated to only run at a known warehouse location.
This is an interesting puzzle. I can't find any actual details via Google, so until someone finds something authoritative here are my thoughts:
First, we need to remember that the Kindle being pre-configured is the default flow, the device being shipped in gift mode without being linked is an exception. This means certainly nobody is opening boxes, setting up the device, and re-packaging them. The pre-configuration is happening domestically after the device has been received by Amazon from overseas manufacturing, since the turnaround is too quick for ocean shipping.
My first idea is that Kindles are shipped in bulk from manufacturing and are packaged for shipping in the destination country, and the pre-configuration happens at that time. This could make sense if Amazon wants to have localized packaging materials, but seems like it would be too much work happening at the destination country.
My second idea is that the Kindles are shipped pre-packaged to the warehouse, but something triggers them to wake up in the box and download configuration information before shipment to the customer. On the simplistic level, booting up once or twice a day at a certain time to check for a known Amazon Warehouse WiFi network with saved credentials, if present connecting and downloading a configuration package with your account cookies. Or having some low-power chip that is triggered by a particular signal on the shipping line, or geo-gated to only run at a known warehouse location.
Edit: From Reddit comments, it looks like I'm wrong on both counts, existing Amazon-branded devices, partner device, and phones with the Amazon app provide the bootstrap network: https://www.amazon.com/gp/help/customer/display.html?nodeId=...