I think the welds are in the middle because that was the easiest place to cut them in the first place.
I'm talking about safety not finance. You just can't fix stupid when it comes to some folks who buy everything at auction. You also can't keep the sellers from being fraudulent which is what it is. That being said, in the period of time between 1968 and 1986 when good M1Rifles were in short supply, many demilled receivers got rewelded and many rifles built using them. Some were beautifully done and some not. The one I repaired and restocked was nicer than the one we're talking about here but it was still pretty obvious. At least to me. Most if not all are functional either way. They're out there so caveat emptor.