Greetings to all,
I’m bugging you once more with the same-but-different intersection issue.
I have these two breps:
I want the trimmed (interior) region, which rhino cranks out without trouble via split:
grasshopper, on the other hand, does not:
split brep/split surface yield the same - I know it’s silly…but why does this happen without a warning? I have learned to accept this in my rhino/gh experience, however there are times that a little bug like this sends you on a rabbit hole 
Here’s the file:
splitbrep.3dm (1014.7 KB)
Thanks in advance for taking a look