A little confusion here. What’s the point of the multiple category filter if it only works by subtracting categories you don’t want?

For instance, I want to only display category 5 & 6 so I input 5,6

with 5,6 listed out I still see every category so it doesn’t really filter at all.

If I exclude posts, however then I can display exactly what I want.

Isn’t the purpose of filtering by multiple categories to display only what you want?