Thanks for the feedback guys!
It uses this experimental feature called /filter, you can see the DSL query in this meta post
This is different from categories because you can create a custom list with 2 categories, e.g., category:bug,feature or, in my case, category:arts-media,feature would bring all topics that include both categories.
I have tested, and from what I could see, tag groups are not supported in the /filter feature.