I've had experiences with all 4 different clocks and i agree you need the ignition on, and that only.

If he is adoment he has to have his lights on, hes either had his cars loom changed and they have got the ignition feed and illumination feed switched over, probably where the A pillar wiring has been cut, or the wiring plug on the clock has been soldered in wrong (the clocks illuminate with either an ignition feed or an illumination feed)