Category checkboxes can work a couple different ways when your features have multiple, overlapping categories. They can be inclusive, meaning that if any of the currently active categories are present, the feature will show up. Otherwise, they can be exclusive, meaning that if the feature has any categories that are currently inactive, it’s hidden.
You can see here that all of the Ski Resorts are also mountains, so they stay visible even when Ski Resorts is turned off.
This is an example of inclusive categories.
https://wpmaps-docs.mapster.me/fundamentals/maps/filters-and-lists#category-filter