Please fix this bug, at least when the question is migrated. This has a larger impact than just mixing up different reasons for closing when migration comes into picture.
Recently, I voted to close this question on cstheory.stackexchange.com as off topic, and after my vote, a moderator of cstheory decided to migrate the question to cs.stackexchange.comcs.stackexchange.com. Although I did not vote to migrate the question, my name was shown on cstheory as one of the users who migrated the question because of this bug:
migrated to cs.stackexchange.comcs.stackexchange.com by Tsuyoshi Ito, Robin Kothari, Artem Kaznatcheev, Dave Clarke ♦ 8 hours ago
Later, a moderator of cs.stackexchange.com saw my name in this list. He (naturally but incorrectly) thought that I voted to migrate the question, and asked me why I did so. It took some back-and-forth to resolve his confusion (hopefully now he understands the situation). This confusion should not have arisen in the first place.