I'd argue though, if you use a single password for everything, its probably more secure to add it here to at least get an indication when it's breached. Your surface in that case is already so large that the difference is negligible compared to the gained warning.
I have to say though, haveibeenpwned is very well regarded in the industry, and is run by a well known security expert. A leak from there would be quite the blow to his reputation.
that means (if your locale is set according to your position), you are probably somewhere in the blue area on this, while I'm in the orange.
https://commons.wikimedia.org/wiki/File:First_Day_of_Week_World_Map.svg