I don't think its a weird decision at all. They support almost 50 editors and are likely to add more. If you were to port the entire application to each editor

I don't think its a weird decision at all. They support almost 50 editors and are likely to add more. If you were to port the entire application to each editor's idiosyncratic plugin API, it would be a huge scaling issue for them. Instead, if you make your application standalone and multiplatform and then turn the plugins into thin controllers to connect the IDE and the application, you save yourself a whole lot of development time.