After all, the Taixu Shrimp itself is a living space creature, and the Earth Mother Fungus lives in symbiosis inside the Taixu Shrimp, at least feeding some nutrients back. The Mo Mountain People are purely hitching a ride on the shrimp's power, parasitizing the giant shrimp to carry out interstellar colonization. The flesh inside the Legion battleship seems to be the same principle—parasitic on the entire Legion, breeding and growing by borrowing the Legion's strength, Titan's strength, and the soldiers' strength.
Not only are the Titan battle-bodies parasitized by this flesh, the crew aboard the ship are all parasitized Hosts as well. Whether Legion soldiers or slaves, spiders, lizards, bald heads—on all these Different World crew members you can see traces of the flesh's parasitism.
