If the correlation had come out the other way, you'd be jumping on it as proof of your thesis that LWers favor MWI because they are sheepishly following Eliezer.

Probably (though not a proof, just one piece of evidence). I suspect that "garbage in" is the reason why we don't see it, but I do not have a convincing argument either way, short of asking Eliezer to post an insincere message "I no longer believe in MWI", take the survey soon after, then have him retract the retraction. This would, however, be rather damaging to his credibility in general.