That's actually wrong. More like the other way round. Australia's time zones are between UTC+8 and UTC+10 with the international date line being far east of Australia in the middle of the Pacific Ocean.
I am in Germany, ordered the Sport SG/black band :07 with confirmation mail at :09. The time frame is also 12-26.
I don't know if this is the justification for it, but daytime hits North America later than most of the world. Australia/Asia is first, then Europe, then North America. I assume Apple is trying to get deliveries to entire world at roughly the same time (or as close as possible).
Wait.. that's right.. so if they deliver to Germany on 5/12, you'd not only get it earlier in the day, you'd be a full day ahead of the US delivery. Sorry, I had to write this down to figure it out in my own head. Hmm.. maybe they are trying to avoid favoritism by shipping to the other continents before North America?
Or maybe it takes longer to ship to the US.

China is about 4,000km closer to Germany than the US.
Another thing that confuses me is why they don't schedule any deliveries starting on Monday, May 11.