Admin themes are common in theme marketplaces. As a convention, they usually always list out all the package UI elements (buttons, spinners, etc) as "components", which is a bit different than in the framework sense.
https://wrapbootstrap.com/category/templates/admin-templates
https://themeforest.net/category/site-templates/admin-templa...
Note the "component" terminology has been used in Bootstrap for a long time: https://getbootstrap.com/2.3.2/components.html