The Bug

The vines on an iron golem's body are all on it's right side, but the right arm has no vines at all. The left arm, on the other hand, has vines all over, whereas the left side of the body has no vines on it.
The legs do have the vines correctly on the right leg, and not the left one. It seems that this was an oversight when the first iron golem texture was made, where the wrong arm was textured to have the vine, accidentally, and just never corrected.

Observed Result

The vines were on the left arm

Expected Result

The vines would be on the right arm