When you look at the texture maps at full size, you will notice that in absolute values there are many more pixels at the neck joint of the head text. than at the neck of the body. This is what makes it more diffcult to get an invisible transition. This is also what distinguishes good texture artists from mediocre ones. The quality level can differ in photorealism etc but I personally find that if you pay for it, this seam must be invisible. So I would complain to the creator of that texture. I would also love it if people who meet such a thing would add a product review to the MP's page of that product.