While that is possible it would make no sense. Why spend time refactoring code to improve a legacy UI for old browsers almost nobody is using? Legacy UI doesn't

While that is possible it would make no sense. Why spend time refactoring code to improve a legacy UI for old browsers almost nobody is using? Legacy UI doesn't know anything about categorization because it was added later. Actually Gmail's approach is sane. They just keep old UI working as it used to many years ago although the backend could have changed completely.