The sculpted neck is the only way you can address the problem, otherwise the neck looses the ability to be lent over to the left or right, and would still look bad in an open shirt. Not as bad, but why have the ball joint between the shoulders if it isn't going to be useful in posing, other than to turn the head. Then Hot Toys may as well just make all figures sculpted necked and provide the adapters for use with other company bodies. Then if they did that, there'd be complaints of older Heads not retro compatible with newer bodies. If they just narrowed the gaps it'd still be a compromise. They'd be sacrificing the sideways neck movement, which isn't necessarily a bad thing to many people.
It's basically a one body for every situation. Where the narrow shoulders TT addresses one specific area that may have been overlooked when the initial TT was introduced, and if that's the case, this looks like being the standard body.
Maybe Hot Toys will pander to more kit bashers by mass producing a sculpted neck TT whenever they think that's a viable thing, but for now they'll just use the sculpted necks on their own figures, knowing if you really want one you'll buy one of their marketed figures, whilst those parting out figures are filling the kit bashers needs for the most part.
Thanks. 
