I had a thought that I can't back up right now but- being a Watcher runs in the family. Love them or hate them, Giles is related to some of them. That could make Wood seem like a distant cousin, sort of. Adopted, but then I suspect the Potentials get to be Watchers if they arent Slayers, so its a family that adopts tons of people routinely. And at the time a really large proportion of Watchers were getting dead. So however many were left you'd hang on to closer.

Raised by a Watcher, trained like a Slayer, but without Slayer powers, makes Wood like a Watcher that got there by the Potential route. If it works that way. But in attitude he does have a big of the rogue in him, so yes Faith overlap.

Like I said, this is a theory skinny on the data, but it just occured to me.