I like to have a select only for one category (in my case for the taxonomy advanced type).
However, using the flatten type "radio_list" missing the visibility of the hierachy of course.
The advanced select is fine, but unfortunately it show all categories flattened.
This field would also have the advantage that it could represent a hierarchy in a very space-saving way - unlike a radio tree.
But both variants would be a good way to get a better overview of the categories and their hirarchy, especially with many entries.
Would be great if you could think about it.