What problem does this address?

Right now the only way for a theme to control the order in which the registered patterns in the default categories show in the inserter is via re-registering the already existing categories. This is even done by TT2.

What is your proposed solution?

It feels like theme patterns are always going to be more relevant to the user than the default ones from core, so it would be good to either have an option when registering the template for the sort order or make the theme ones show up first by default.