From what I read, it wasn't even a type of wood that was banned. It's a maple bat, which is legal, but it's illegal if it's not dense enough. Maldonado would have had no way of knowing, because maple is one of the popular wood types in MLB and wouldn't have stuck out as different.

Lower density maple allowed for a bigger barrel profile while keeping it from swinging too heavy. This is just a preference. It's not an actual advantage because as long as you're using quality solid wood, every possible factor has a tradeoff. Players just swing what's comfortable and what compliments their approach at the plate.