<p>It's not impossible just unlikely to have been the case for all of them, I mean maybe some of them might've been on Homeworld as moles for the Crystal Gems and when they heard the Earth was decimated they could've decided to run away to the caverns of Homeworld. But there's not much backing it up. Fluorite at the very least I can believe having a component who was present during the war because of her many components and having lived for so long, as for how else they could've known about Earth well Rhodonite does have a Ruby for a component so maybe her Ruby half faught in the war. </p>