NPC controlled resource bases

I've been wondering about this a little recently, this is more of a game theory post than anything. If you check out this old post on the official forums and scroll down slightly, you'll see a table indicating which resource bases will be npc controlled (unowned) when you first uncover them. It really helped as I was leveling up, because then I'd know which bases to uncover first when I upgraded my radar. The table was right 100% of the time, and the bases which were supposed to be NPC controlled were indeed unowned.

But it got me wondering, if certain resource bases are always NPC controlled at first for everyone, then why would they ever be attacked by a human? I'm fairly certain (but not positive) I've had resource bases which were originally unowned when I first captured them attacked by a player later on. It just doesn't make much sense to me, since you'd think nobody would reroll an NPC controlled resource base since they're so easy to capture. Anybody have any thoughts on how this works? Or I suppose the more basic question needs to be confirmed first, have you had resource bases which were originally unowned attacked by other players?