This doesn't reduce the need to type all that again and again, it only makes Visual Studio's IntelliSense recognize such when working with templates.
The developer has to type sample template arguments for it to work.
Not very time/effort saving IMO.
Until this is actually out of preview and I have some time playing around with it I don't see fully the usefulness. Maybe it will be something better than sliced bread.
Well, that's my point. If your template happens to need to work with such types, you're SOL. Either type that whole thing in, or don't use the feature.