I see what you're trying to say since you can't be using the same N-P-K for both veg and bloom but Ginormous is technically a bloom booster since it only contains P and K. If you cut off the Oneness, you are also cutting off the N, Mg, B, Cu, Fe, Mn, and Zn since Ginormous alone doesn't provide any of those essential elements. It seems to me that the Ginormous is added only to boost the P and K values of the base nutrient to make them better suited for a flowering plant's needs.
The pre-harvest flush should get the excess nutrients out of the plant. Starving the plant weeks before this is only going to adversely affect yield. Most of the advice thrown around by the burnt out stoners making minimum wage at the hydro shop is laughable at best.