I don't think anyone doubts that - but it is hard to get faster at planning (and usually a bad idea), while it is very possible to get faster at typing/editing

I don't think anyone doubts that - but it is hard to get faster at planning (and usually a bad idea), while it is very possible to get faster at typing/editing (the latter benefits a lot more from knowing an editor than the former). So if you want to increase your productivity, you might as well go after what you can reasonably expect to speed up.