Isn't this an example of an abundance of empathy? If the user has requested dark-mode, websites responding with their best version of a dark-mode experience is an example of user empathy in action.
I operate in dark-mode 24/7 myself, and I've been pleasantly surprised at websites slowly supporting a dark-mode experience and automatically showing that by default.
There should probably be a one-click "override dark/light mode on this site" button somewhere, so that you don't have to dig into your OS to change it back. But the defaults here seem like the most reasonable, most user-respecting thing that could possibly exist.