I didn’t mean it was a daas yochid to rule that one must wash on even one slice. Many poskim ruled as such long before this survey. And many people have washed for one slice long before this psak. See:
I meant the methodology itself of looking at general non-Jewish society for this purpose is unusual and apparently daas yochid, assuming you’re correct in relating that the survey was the decisive factor in the psak. Most poskim wouldn’t accept considering non-Jewish society in determining the psak for this purpose.
Various other poskim ruled it mandatory to wash on one slice long before this survey for reasons other than what the goyim do.