Low oil pressure?

I don't understand the oil line in the valley mod it makes no sense to me, I would block off the oil to the left side if it has solid lifters and that would give more oil to the mains, the lifters get drain back oil from the top and oil from the rods from the bottom there is no lack of oil.
I used to do it that way. Works fine for regular roller lifters.
Are you referring to the crossover line for improved main oiling or the new one for better rocker arm oiling?