Hmm it may be the software I use (Tekla) how it exports it.
At first I tried to run a seam in the exact spot yours are, but my objects were tubes with a hollow bored in it (a Circular Hollow Section)
So I changed it to just a Round in my software then exported again, now when creating seams and peeling all I get is like a Plane peeling with a few nodes and no unwrapping (like paper) if that makes sense?
That is the model I’m trying to unwrap