The squirters will not function as a pressure relief valve; they just act like a small leak in the oiling system. Also, my Pond blocks have both been drilled for the factory pressure relief valve, but they have not been needed because the opening between the side oiler gallery and the hole for the pressure relief valve is not open on my blocks. I would think that all Pond blocks are this way. I think if you wanted to use a pressure relief valve in the Pond blocks you could, but you would have to open up a slot between the side oiler gallery and the hole for the pressure relief valve.
Since all the stock and aftermarket oil pumps have a pressure relief valve built in, you can certainly get by without using the pressure relief valve in the block.