Ah okay, got it. Yeah so I thought maybe it was discontinuous with subd, because deleting a point combines the edges together, but I see now that if you extract that control polygon you are kidding yourself and rhino will redraw the tris/quads after rebuild mesh. I just took a mesh box and subd box and looked at the result of deleting a few edges.
I guess what I’m really trying to say is, is there a way to delete an edge loop on a plain old mesh? If you make a mesh box into a subd, delete the edge loop, and extract, you can. My reason for asking would be that you can delete mesh edge loops without realising you’re actually not having any effect really.