What they're saying is that the wort needs to be cooled before you add the yeast. It doesn't matter at all when you add the water - you can add it in the fermenter, or add water to the kettle and pour the whole mix into the fermenter. 6 of one, 1/2 dozen of the other.
The only thing you DON'T want to do is pour hot wort into the fermenter because plastic will warp and glass will be thermal shocked. You can, however, add your cold topoff water to the fermenter and slowly add hot wort so that the temps equalize to something safe.