I don't think they're complaining about drug dealers paying part of their forex bill for them. Colombia has done the same thing for the past 50 years too (Google "black market peso exchange" or "sinister window"). But they probably don't like that high level people can have assets they don't know about or can't touch when they're in the process of a big corruption crackdown.
It’s not just high level people moving capital our of China. It’s any well-to-do Chinese. Look at what happened to Vancouver. Basically a lot of people wanted to bring their cash out of China to avoid things like taxation, government crackdowns, etc. in general just protect their wealth because western governments are more predictable and friendlier to wealth inequalities.
But more importantly, all of that cash going to Canadian real estate and property owners is money taken out of the domestic Chinese economy.