I've had it happen a few times to me. I don't think I've ever had both new villagers with skills, though; one of them has always been untrained, like the pair who fall down the waterfall at the start of the game.
I thought that also. Each time I had this event, always one of them was skilled. But in my last tribe, it happened twice and, the 2nd time, the new villagers were both trainee farmer!
