In Peter Von Brackel's excellent Paperweights Historicism Art Nouveau Art deco 1842 to Present, a very nice "basket" weight is shown on page 25. It has millefiori, two torsades and a handle made from the same coloured twist cane. The millefiori canes are "Silesian / Bohemian" and the base is star cut. It is said to be a "rare motif from this area" - whether that applies just to the basket form or also to the use of a torsade (or "staves") I'm not sure.
I think the "extended air bubble" above the torsade in Roy's weight is pretty much as Leni said. Probably the result of not marvering in the torsade therefore leaving a clear recess at the top edge (and probably also underneath, to some extent) which, in taking the next gather of glass has trapped air in a neat ring around the weight. Deliberate by design? Or just a pleasing effect?