Ive just been to double check mine again, and the only button that gets covered is the power button, but the holder part where the power button is covered has a groove in it so the holder applies no pressure to the power button

The volume keys and all other buttons on the phone and speakers all have cut outs on the holder part so are not covered at all

If you put the phone in the holder the other way round you dont have the groove for the power button and the volume keys are covered too

The release clip is where the top of the phone goes (with the usb socket)