>>simonw+27
I'd guess so, yes. I think dark mode users leave the screen brighter than it should be, because in dark mode, it doesn't matter as much as it does in light mode. Then, after looking at dark things for a while, the eye gets used to the light level, and then opening a white page is like a supernova happening in front of the user's face. In short, with dark mode, the lightness baseline is much lower, and a light page disrupts this.
I'd say it's more of a courtesy thing. If you like a bit of a web design challenge, you can experiment with the prefers-color-scheme CSS feature. With this, the browser will automatically apply the dark mode for users that have it set, making the experience seamless (and state of the art).