Child Theme Filters

I tried to view a list of child themes that were suitable for the Real Estate Theme but when I went to the Child Themes Main Page and selected the filter / option for Real Estate ( or any other option ) it just displayed exactly the same child themes. Is this a bug or is it meant to work that way ? To see what I mean then go to the following link and select any of the category filters : https://childthemes.premiumpress.com/themes/real-estate-theme/