Just to avoid misunderstandings: what the cat freaked out over was actually the box that held the pieces. I do not know for certain that the box is actually made of olive wood. I do not know for certain whether it's the wood of the box or the residual smell of one or other set of pieces.

I do agree, though, that it seems fairly clear that great freshness isn't needed. The set wasn't terribly new when the cat that freaked out over it joined the household.