It seems to me, that design is much more forgiving when it comes to fit.
No matter what, the neck will touch somewhere.
If the neck is too wide, it will touch the sides, but not the bottom.
If it's too narrow, it'll touch the bottom, but not the sides.
On a regular bolt-on, too wide means it won't fit, too narrow will show a huge gap on the sides.
Maybe that's just me....