I’ve run into some similar issues — I’ve learned to differentiate the two boxes over time, but at first I was definitely accidentally clicking into the preview pane by mistake.
I’ve wondered if something like this would work to de-emphasize the preview a bit… but changing the background color does make it mildly less accurate as a preview; and there are likely some issues with custom theming that would arise.
There was some good thought here that may be enough to make it a non-issue.