Split brep failure

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 :slight_smile:

Here’s the file:
splitbrep.3dm (1014.7 KB)

Thanks in advance for taking a look