There is a little incorrection where it says "the Progenitors left their three Cores hidden". It gives the impression they did on purpose but the game is clear in the fact the three Cores were scatered after a Foundry ship was destroyed. It's also unclear the three Corws were the "only" Cores as well, though it's true in the realm of Homeworld2 the quest is to find tech on the remains of the before mentioned Foundry ship. So the text should be "Progenitors left three Cores scattered on the remains of an ancient vessel".