Bear in mind that some contrarian statements might have been upvoted for being valuable as examples and contributions to the thread, rather than for substantial agreement. Also there is a selection effect: a contrarian sharing an unpopular opinion is very likely to upvote it when seeing a kindred spirit, but a non-contrarian who doesn’t share it is unlikely to downvote it (especially in a thread like this one where the point is to encourage contrarian opinions to come out).
I’ve up-voted several lists containing statements with which I disagree (some vehemently so), but which were thought provoking or otherwise helpful. So, even if this is just anecdotal evidence, the process you described seems to be happening.
Bear in mind that some contrarian statements might have been upvoted for being valuable as examples and contributions to the thread, rather than for substantial agreement. Also there is a selection effect: a contrarian sharing an unpopular opinion is very likely to upvote it when seeing a kindred spirit, but a non-contrarian who doesn’t share it is unlikely to downvote it (especially in a thread like this one where the point is to encourage contrarian opinions to come out).
I’ve up-voted several lists containing statements with which I disagree (some vehemently so), but which were thought provoking or otherwise helpful. So, even if this is just anecdotal evidence, the process you described seems to be happening.