Hello there A. Oliver, and welcome to our forum
Yes, I have never seen a Melo pearl in half, being so rare and valuable I cannot imagine anyone trying to cut them in half!
But all pearls are formed in the same way by the same organ (the mantle) so they all have the same inner structure: that of an onion cut in half.
So, that image you posted of the natural pearls in half is very much accurate for a Melo pearl.