Remember that the first thing that yeast does when it is put in wort is multiply to an enormous population. Knowing that, it makes sense that adding more yeast is a good thing because it gives the yeast a head start, right?
Yeast isn't really an ingredient. You are introducing a life form to a nutritional medium that is reasonably devoid of life forms. It will do what it wants from there.
Oh don't give me none more of that Old Janx Spirit
No, don't you give me none more of that Old Janx Spirit
For my head will fly, my tongue will lie, my eyes will fry and I may die
Won't you pour me one more of that sinful Old Janx Spirit