Not at all. I've been kind of a 40k-phile since I was in grade school. I've been playing Dark Heresy off and on for maybe three years or so with a steady group of people back home, but mostly as a GM and never as a player. Most of the stories I wrote didn't revolve around xenos, so I didn't really consider their behavior much, let alone just Kroot. Now the group I've started playing with has a steady GM starting up a Rogue Trader campaign (which I've GMed once, just the Into the Maw adventure from the Core book), and immediately jumped at the xenos careers. It seemed a little more challenging, but also the Mass Effect I've been playing has influenced me a bit, too. I found it pretty odd that I had never even considered a xenos character before, disregarding it out of hand, and was surprised (but relieved) to see something official come around.
So, yeah. I'm not new to 40k, just to Kroot behavior.