Ever tried to use continuous agitation without either a motorized processor or, at least, a hand operated roller?
If you had, you will know one major reason why intermittent agitation is one of the recommendations.
Kodak, for their part, provide data to those who use motorized continuous agitation.
If you don't agitate at all, or use very little agitation, the development isn't uniform, due to local developer exhaustion.
Sometimes that unevenness is quite subtle - leading to little more than enhanced edge effects - so minimal agitation can be a useful tool when employed carefully, and with knowledge aforethought.
Too much agitation can lead to increased contrast, more obvious grain and developer oxidation. Developers are designed with a certain amount of agitation in mind. Why waste all the work that went into that design?