He only scanned his back. Although the green light seems to go all the way through and copy the other side of his body, it seems to estimate for the rest of his clothing. This is why Dipper clones have no bow tie and no hat symbol - neither can be seen from the back.
This is further backed up when you notice that you can see that his hat has a white portion from the back, but you can’t see what’s on it. Hence, blank white portion.
My headcanon is flawless.