wandererfan wrote:but I don't know what would be the objection to having both boxes ticked.
I know the answer to that because I thought the same thing and ask Werner about it when he first made the tool.
What it is, is a toggle between the type of surface to be produced either being Ruled or not, regardless of the Loft's producing a solid or a surface. For anyone who does not know, a Ruled Surface is a geometric principle, it is a surface that can be described but straight lines, if you don't know what I am talking about, have a look on wikipedia, it has a great article, search "ruled surface".
So Loft can produce a solid whose sub-component surface is either a ruled or not ruled, surface. Loft can also produce a surface only, that is not a solid, but that surface can still be either a ruled surface or not ruled surface.
My testing of the latest FreeCAD 0.14dev code both compiled against occ6.5.0 and the same FreeCAD code compiled against OCC6.7.0 (OCE0.16) shows that the "twisted issue" you found in Loft only happens with the later OCC.