Shell not exact?

 From:  Michael Gibson
5385.15 In reply to 5385.9 
Hi Rudl, also probably if you had the original object a solid the offset would work ok in MoI too, since then the assumption of "one input vertex generates one output vertex" would hold true.

It's in this case of a non-solid object with open boundary edges like you've got here where that "one input vertex generates one output vertex" assumption does not hold true anymore, and that's when MoI will produce a badly formed result, it will have just one vertex in there instead of it branching out into more than one with a new edge between them like you see in the TC result.

So the actual goal for what I hope they'll be able to do to improve the offsetting is to actually generate I think the same result as what you don't like from TC...

- Michael