Mine arrived today from simplygames but I don't see why it's an issue if it arrives later. It's not as if you can access the new content yet, I think mine will be staying in the wrap until Tuesday.
Because some of us haven't played it since vanilla and wanted to be able to get up to par with the previous 2 expansions ready for when TTK unlocks.
I was going to buy the digital edition for this reason until they said my order was shipped. They then cancelled it 2 days after saying it was shipped so now I don't know what has happened and if I buy it from PSN I might end paying twice. As it stands I probably won't have one copy.