Ask your LOR. R' Shlomo Miller holds bourbon is never a chametz problem as it must legally be over %50 corn thus being chametz dirabanan which will not be a problem. Heard from him personally.
Not doubting your quote, but would be considered to be a chidush since there commonly is chametz (fermented barley) which is an integral part of the process it wouldn't be batel. That is the opinion on the AKO, which represents most North American Kashrus Organizations. This seems to be clear in the Mishna Berura as well (442:27).
http://www.crcweb.org/Whisky%20Alert%20with%20Q&A%20(Sep%202010).pdfIs it possible the question posed to Rav Miller was from someone who already owned the questionable bourbon? That would be very different, because we are meikel on chametz sheaver alav hapesach derabanan in a case of hefsed. that would not apply to someone who was buying it already ipso facto.
It may also be true that the well intentioned person who did the research on this did the community a disservice since there isn't really a chiyuv to be mevarer the ownership. But once it's done it's done.