So far only three component types are supported because they are the only ones known to work. However, other block types like drag and drop may work fine. What's needed is for someone to test content libraries with other block types and then add them to the list of allowed types (or remove the restriction if we find that most block types work correctly).
If you'd like to take this on and submit a pull request, the code that limits what block types are allowed is
here, although some corresponding changes to the Studio UI are also required.