I don't know that we ever saw a pre-Phyrexian Gith. Maybe he hadn't been modified yet, but he was one of those monks who worshipped the artifacts and had started installing them in his own body hadn't he? I don't remember there having been a time when Phyrexia didn't have its hooks in him. Geth by contrast started out as a purely selfish warlord, long before Phyrexia displayed its presence on Mirrodin (ie before they retconned it as having been present all along).