Hi Burr, somehow the top edge on the bottom edge is not a closed curve, if you zoom in real closely you can see that the start and end of the edge do not quite match:





So that's why the seam adjuster points do not show up, you only get the seam adjuster when all the curves being lofted or blended are all closed curves.

You do still get the flip control inside of Blend though, which is available by clicking on the blend edge while you are in the Blend command - that will flip the orientation used for the edge you clicked on, so one click on one of the edges while you are at the "Adjust blend parameters" stage of the Blend command should fix it up.

But the surface itself seems to be closed, something happened while trimming or cutting it that jiggled its edge curve slightly at the end, but you can repair that by doing an untrim to get a fresh trimming boundary created on it. To do that select all the edges (select 1 and then do Ctrl+A), and hit delete, that will remove the current trim boundary and use a new one created directly from the underlying surface and that will get a proper closed edge curve on it then and behave like you were expecting.

Hope this helps!

- Michael