As the title says my 32-bit HDR files open as 8-bit in Camera Raw 7.3. I have a Win 7 32-bit system. I create the 32-bit HDR and then save it as a 32-bit TIFF but when I open it in PS CS6 via Camera Raw 7.3 it comes in as only 8-bit.
As far as i know acr won't output an 32 bits/channel file (hdr), but you should be able to change acr so photoshop gets a 16 bits/channel image by clicking on the
Workflow Options at the bottom of the acr dialog and set the depth to 16 bits/channel.