It's true. The human brain cannot fabricate faces or other human characteristics. Every face of every person you see in a dream belongs to someone in the real world that you've met before. Your subconscious has an insane memory for this sort of thing.
Lucid dreaming is actually overhyped and overrated. When you're lucid dreaming, you just feel like you're thinking really hard the whole time. And that's because you are. It's all in your head, and it's actually a little exhausting.