The key word that I read was new. Remember, a new deck lumber is often too green and ful of liquids to even think about staining yet. In my region, a new deck needs about three to four months to dry out before any think can be added to it. The idea is that the new lumber has to leach out the liquids in it and if its stained or sealed, the sealant will leach off with the moisture. So wait until its totally dry, then use your sealant.