An Atmel microcontroller is not crypto hardware, and this group buy started Aug 2nd. so there has been a lot of time to organize components.
Do a google on Atmel distributor Australia and you will see that Digikey is not the only player.
1. Maybe barntech & co didn't have the funds to secure all components at once?
2. He mentioned in his post that they ordered from Digikey because they where the only ones that could deliver the amount of microcontrollers they where after.