Photoshop as a Export 3d Layer command in the 3D menu. I selected 3d PDF as the format.
Ok - I created my own test file and now know what's happening. When Photoshop exports the 3D PDF, it adds some JavaScript to the model that overrides the default view and resets the camera position, lighting, and render mode. It will run every time the model is activated the first time after you open the file or hit that page.
You can remove the script by opening the 3D properties dialog in Acrobat, go to the "3D" tab and hit "Clear" in the "Script" section. Close the dialog and save the file. I haven't seen a way to stop Photoshop from adding the script though I didn't put a lot of time into it.
Without the script, your view settings will work normally.
J-