Exactly. It's that pesky causation vs correlation thing. Blinking wasn't likely causing voters to vote one way or the other. Something else may have, or else it could just be a random correlation.
I chalk it up to an "insufficient sample size" thing. They're trying to infer a trend from only 8 instances. As the article notes, when we also consider primaries, the trend gets a lot muddier.
I can see plausible reasons for a correlation between blinking rate and campaign success. I can't see plausible reasons for why this effect would be present in presidential campaigns but not in the primaries.