Heh, heh... I guess the following experience isn't up to "the guy at the bike shop":

• 35-years wrenching on bikes, from BMX to building my own carbon-fibre bike
• professionally built 14 custom-frames (10 crit-bikes & 4 track-bikes), too late in the market for torch-wielders.
• 10-years working in a shop
• built over 1000 wheelsets, sometimes having to custom-cut and roll my own spokes
• 3-years in Mavic support-van, doing everything required of a shop-employee, but 10x faster. Heck, I don't know of many shop-employees who can pull out a torch and replace bent/broken dropouts in a frame from a crash, then have it all cleaned up, painted and re-assembled by morning for the next race.

By the way, if you put a little ink/grease on the contact-surfaces of outer-nuts of the QR to mark where they touch the dropouts, you can see that the "footprint" of the QR is exactly the same on both sides. From the wheel, axle & dropout's viewpoint, they have no idea which side the QR-lever is located.