I just searched for Radiohead and viewed all albums. Most of them are cover albums like lullabies and Strung Out On X, but these three were all right next to each other. You can see the pre-order price button and release date on individual item pages too, like this one for IN RAINBOWS: http://smile.amazon.com/dp/B01F0K1WQ0
Not sure if that maybe has some slight connection to what's happening right now. Here's a link to In Rainbows: http://smile.amazon.com/dp/B01F0K1WQ0
I'm really hoping that it's only physical. The digital re-release of In Rainbows is still May 6th.