I have not worked at Google and have no idea what the list in question is, who maintains it, or what it takes to get on said blacklist. Speculation admits a lot of possibilities, including your own, but there's no evidence that managers created that list. It could well be line staff producing and publishing their own list of preferences. As a random example, perhaps a list of known sexual harassers that HR has not acted on, curated by an individual contributor with a victim's right's motive, and shared with at-risk coworkers. In such a situation, a person might legitimately wish to not put themselves in another stressful, high anxiety situation involving harassment.

Either option and many more are possible. All the ones I can think of suggest that Google's hiring and transfer process needs work.