Retina support for header background image

Hi
I’ve seen you support Retina https://www.kadencewp.com/blog/post-frequently-asked-questions/ but not sure if there are any restrictions.
I have added a header image in theme options – advanced styling – header background – Upload background image or texture.
On loading the page in chrome developer I don’t see src or srcset (I do for other woocommerce pictures which have @2x file paths in the srcset) so am not sure that retina support is working for this header image. The only reference to the jpg is this:
.headerclass {background: url(http://localhost/wordpress1/wp-content/uploads/2019/10/my_banner.jpg) ;}

Thanks