Can nutritional yeast flakes be used as a bread leavening?
Well, your own link states clearly:


  When the yeast is ready, it is killed (deactivated) with heat and then harvested, washed, dried and packaged.


So no, you can not use nutritional yeast to leaven your dough. 

Only live yeast manages to create CO2 bubbles as byproduct of its digestion. Many novice or careless bakers inadvertantly kill their yeast by using too-warm liquid - and end up with a dough that never rises.