I don't think it's that simple.
I see it as similar to acting. Some actors are superb at putting on different masks to suit different roles, and you'd be hard pressed to guess if any of them reflect the person underneath. But some actors are essentially the same regardless of the role - and this applies to many famous actors. But this doesn't necessarily mean that what you see on the screen is the real person - sometimes it is, but sometimes it's a mask, but the actor only has the one mask and they don it for all their roles.
Reading non-fiction articles by, and interviews with, favourite fiction authors can be surprising, you sometimes discover they aren't what you might have imagined. Or it can be an affirmation that they are exactly what you thought. But, as with actors, you don't actually know if they have simply donned the same mask for their non-fiction or interview.
So, while most writers do develop a distinctive and recognisable voice, I'd say the concept is too nebulous to make assessments about their personality or soul. We might recognise the voice and form guesses as a result, but the guesses aren't reliable, and the answer will vary from author to author.
So, since you don't have "It varies" as an option, I don't think I can vote.
