I found a bug in the Boundary Surface component. The output surfaces are in a different order than the order of your input curves.
The funny thing is that if all of your curves have the same direction, this issue doesn’t occur. Also if you first graft the Boundary Surface input and then flatten the output it works, but that defies the parallel aspect of the component.
See attached image. The numbers in White are how the ordering should be, the Green numbers are from the first graft than flatten method. And the red numbers are what happens naturally with the component and as you can see they’re off.