Wow. Never thought of it this way.
Always used right eye. My right eye is nearsighted and my left is farsighted. With glasses, everything is OK; without, passable.
Use right eye w/ glasses on all SLR's My point 'n' shoot has a diopter correction built in, and I set it for my right eye w/o glasses. The magnifier in the waist level on my Kowas seems to also work well with my right eye sans glasses.
However, my most recent toy is a Fuji GS645 rangefinder. Since age has allowed me to have just the faintest beginnings of cataract in the right eye, the left eye works muuuuch better with the Fuji's rangefinder. Fortunately, the viewfinder on that machine is in a good place for the left eye.
I learned 35mm with an old Zeiss Ikon that had "blind" scale focusing. You know, that worked, too!
As for the test in the original post, I was left eye the first time, but now that I'm aware of what's happening, I can go either way ...