Ooor, someone had to "survive" their family's bullshit and being unseen was the best way to do it. Then it became so ingrained in said someone's existential fingerprint, that they're now a ninja without even realising it.
Yeah I'm like this and it's not really a trauma thing for me. I'm just autistic and ADHD which basically means I take advice too seriously and I have a bad habit of getting into someone's field of view or in their way by accident. As a result of being advised to be less visible every time I got in someone's view, I accidentally became invisible. It's something I've been working on lately actually and I've noticed I scare people less often since I started thinking about it
You don't need to assume that it isn't a tragic familial background, either. Or any other sort of trauma/condition which would push one to close off. Throwing the "soulless" label aroud willy-nilly is just an extension of abusing the "narcissist" moniker. It prohibits any nuance and facilitates unjustified suspicion.
Yes, there are sociopaths who can be considered soulless. But just because one is odd does not intrinsically mean one is soulless. There's a plethora of other potential reasons.
Plus, don't forget, oddity is in the eye of the beholder in the first place. My odd may be completely different than your odd.