2D Offset Section Questions

I have a couple of questions regarding the 2D Offset Section option in the Drawing.

I am running CREO 3.0  M090

I have created an offset section in my Assembly using the View Manager.

the Sketch defining this offset section is a closed rectangle.

when I exit the definition phase I get a warning "Created section must be open chain with two ends".

The resulting offset section is exactly what II want.

when I apply this Offset section to a Drawing view, I get exactly what I want in the Drawing.

what does the warning "Created section must be open chain with two ends" mean?

Does a closed offset section cause problems downstream?

I am a little confused since CREO 3.0 lets me make these offset sections and apply them to a Drawing view.

What am I missing here?