Wow, that’s amazing that you’re seeing the “preparing to ship” notice already, and congratulation! I’m surprised that there would be any action 11 days before official release day. I wouldn't have expected anyone to see shipment anytime before the 14th or so, allowing a week to get to your location from China.
My delivery window hasn’t changed from June 4-10, despite ordering only about 1/2 hour after the earliest possible time. When I placed the order, it said “ships in 3-4 weeks”, or May 21-28, but there is no shipping window shown anymore, only a delivery window.
I hope that mine doesn’t slip any further, and either stays within the window, or arrives nearer to the earlier end of the window.
I ordered directly from Apple btw. 12.9”, 500 GB, Space Grey, no engraving.