I guess you are right, but it makes it more interesting if the picks are not almost all from the recent past. On the other hand, I would also guess that spreading the picks evenly across the time range might result in many being from times with little data to differentiate them.
It makes the premise of the entire site flawed, though. And it defeats the purpose of the convenient button provided to redraw a year. That is what should allow you to find a pick that might be more interesting, rather than messing up the randomness promised by the site and the HN title.