duplicated result when using BRep|Plane intersection

Consider the following scenario:

Create a box at (0,0,0) with its bottom face horizontally lies at z=0.

Create a plan at (0,0,0) with its normal being (0,0,1).

Use BRep|Plane component to find the intersection of those two

Result: You get two exactly same intersection curves at the bottom of the box.

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I have also tested this in SDK using Rhino.Geometry.Intersect.Intersection.BrepPlane() and it would give me exactly the same result. It is easy when I only have one box and a 1-dimension list of planes. However when the model structure becomes complex and i don't want to waste computation time for duplication/collision tests. 

Has this occurred to you often? Is it an old question that has been asked and answered many times before already?

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By the way there is a second question, that is in Visual C#, when I was using  AreaMassProperties.Compute(Brep b).Area in order to get the area of a surface, I got 0 for all the results. This is less of a problem though because this method works fine in C# component when I'm in GH instead of VS. Also there is existing component in GH for area calculation already. However I think it's still worthwhile to bring it up.

Thank you!