I disagree with your argument as stated, as offering promotions in exchange for sexual isn’t uncommon, and many times isn’t really a choice.
But I also think this perspective isn’t really the point. Regardless of the abusive nature, it’s still a tremendous conflict of interest for an affair of this nature to occur. The direct report would have a huge amount of leverage over Huang to keep the affair secret for one thing.
I don’t know the nature of these particular affairs, but regardless of who is or isn’t vulnerable, it’s still wildly inappropriate, and shouldn’t be tolerated