In education and games subcategories are available in the freedesktop standard. according to that the application launchers use this subcategories.

I'm not a big fan of the subcategories cause of the problem that e.g. LO calc will be in education in two subcategories. In my point of view the separation in the main categories are enough.

If we come to the soulution that the app launcher should not use subcategories I will add an bug report.

While sub-categories may present challenges for one or two applications, I'm not entirely sure removing support for subcategories in violation of the freedesktop standard is the right solution. There may be instances where subcategories are useful. Rather, I think we should focus on just better categorizing the applications themselves.