Background color of widgets

I saw the Design great Widget. The calendar widget in dark mode, featured at 14:10, was with a gray background, but the current beta version of the is black. Is this a bug? Black background color in dark mode (e.g., calendar, screen time) and gray background color (e.g. (e.g., music, reminders), and since I don't know which one is correct, I have to unify I would like to have it.