In snapshot 14w21b, when you place your 6 wood plank blocks to create a door, it shows that it makes three, and it does! It might be because of the addition of the Iron Trapdoor, but i'm not a minecraft expert. The glitch also happens with iron doors. And now it makes one trapdoor, I just tested it. So, when you make a door, it gives you three, and when you make a trapdoor, it gives you one, I hope this helps.