That’s actually highly surprising! It should be independent of your normal UV channel. Maybe the bounds for local X/Y are somehow off for a skinned mesh? That looks a lot like it thinks “0” is in the right seam of the object, when the offset is supposed to place it smack in the middle.
Actually, maybe the problem is that “Scale UV by center” or “Clothing Pattern Mask” doesn’t like negative texture coordinates. Try adding 0.5 to the U coordinate after dividing by 6.2832.
Try using a regular texture sampler just to make sure it looks OK first.
Triplanar will always have the blend artifact problem. It’s good for rocks and terrain, and for highly angular objects, but not soft meshes IMO.