Based on your advice, I have re-loaded, but I still experience the same variation in behavior. Interestingly, if I go to a 2D drawing in a different window, I see my old expected behavior. (I also don't see any 3D options there. What did I do to use the 3D tools in my new drawing, and why are they (Render, Camera, Examine, Perspective, ...) not available in my simple 2D drawing?) A New from Scratch drawing seems to permit 3D drawing, and also has my old expected behavior, so clearly I have caused this, I just don't know how to uncause it.
Thanks for the help,