Well, I learned something - but it doesn't help me much. Maybe it will help you to help me...?
I am guessing the absence of the tangency selection breaks the edge's ability to be used as a guide curve.
Maybe it is "just one of those things..."?
I will try to create my 3D sketches before the delete face and hope that:
#1 the Loft will work
#2 the edge of the loft will knit to the "finger"
#3 I eventually figure out how to drive this software
Why did you use 3D sketches and not the edges? Any time you Convert Entities or use something other than the edge itself you introduce the chance of errors creeping in.
Are you quite certain that there isn't a very short edge (like 0.004 mm) introduced between the two original edges?
Boundary Surfaces are usually more robust than Lofts. I think about the only place where a Loft still makes sense is when you can do a Centerline Loft. No doubt there are individual cases where the general rule doesn't work and a Loft works best. I suspect that this has nothing to do with your problem, but it is a good rule of thumb to keep in mind.
There is no way to change the accuracy of the SolidWorks model. There is at least one place where you can do something like this, the Knitting tolerance under Gap Control on the Knit Surface, but that is the only one I can remember now.
I don't really understand why SoldiWorks sometimes struggles with accuracy issues. We just have to live with it.
Can I come and work next to you for a week?
I chose not to use the actual edges because I only need half of the edge to create the surf I am looking for. see:
I did try to use boundary, but I had trouble with the outer edge not wanting to be selected. I am not certain there is not a very small edge - but I did zoom "all the way" in to look closely at the vertices. I will take your comments to heart and continue to hone my skills. I prefer boundary blends over sweeps and lofts in Pro/E, so doing the same here will be easy. Another similarity between the two CAD's : strange struggles with accuracy... Nothing new under the sun.
Thanks for your input...