This is a test for SC 1.4.11, with an example of styled background and un-styled focus indication.
The SC and exception state:
User Interface Components: Visual information required to identify user interface components and states, except for inactive components or where the appearance of the component is determined by the user agent and not modified by the author;
My argument is that we've explicitly defined both components AND states as requiring sufficient contrast, but the exception only applies to components (and not explicitly states), otherwise we would have then had the following exception language:
User Interface Components: Visual information required to identify user interface components and states, except for inactive components or where the appearance of the component or state is determined by the user agent and not modified by the author;
Visible tab focus is a state, and that is not called out in the exception, so it is exempt from the exception. I always read this as being for components like an unstyled submit button: