That looks normal. Same here...
Tiles always jump to the 4th column for some reason. It seems we're not allowed to make full 3-column tile groups. Unless someone figured out some tweak for this.
I've played around with it, moving the tiles around and clicking the little "-" minus symbol in the bottom right hand corner and have come to the conclusion that the Start Screen is designed to setup tiles from left to right in their specified block(The title names you give) as pairs and not up and down.