0 dB pan law with and w/o bypass

I am running Cubase Pro 8.0.20, playing back a stereo file with everything bypassed (inserts, sends, eq, and panner) on Mac OS 10.9.5. No effects, no mixing, no panning of any kind - just straight playback of 16 bit 44.1kHz audio.

If I set the pan law to 0 dB, and then A/B compare switching only the panner bypass on/off, I believe I am hearing a difference in the stereo image. However, since I am doing no panning/mixing of any kind, I do not have an explanation of why the stereo image would sound different between the panner bypassed and the panner turned on (set to any pan law).

I am however grateful that it is at least an option in Cubase to bypass the panner; I do not see this option in other DAW programs.