Treat it as a data point and make your own decisions (he does back it up with several sources that indicate a workaholic mentality with that expectation for others). Hiding it ends up perpetuating the behavior unseen.

*Below is an aside that explains why I think it's better to air these things even if it seems like "rumors and gossip."

I know first hand how toxic some people are irl compared to their public persona. There was a professor in my department during my PhD who was known to be a slave driver, but there are no accounts of it outside of the department. We would have to warn incoming students about working with her, though sometimes they wouldn't believe it could be as bad as we said. I spoke with one of her students after she left the lab due to being hospitalized for exhaustion from overwork: the professor contacted her while she was still hospitalized and asked her to complete a task ffs!