RE: "Furling is a product of twisting". Yes, and no. I follow your thinking; however, "rope laying" is the perfect example of furling, and ropes are made of from two to many strands; and their making is a 'one-step' process; not two as many leader makers employ (first "twisting", and then "furling"; both of which are simply twisting operations). The significant difference is that in rope making (laying), this is accomplished by twisting both ends simutaneouly and in the same direction. Thus, the strands are both "twisted" and "furled", in your context, at the same time, as opposed to the two-step process conventionally used when we furl our leaders. Thus, there is no difference between "twisting" and "furling" in my response as you state. Incidentally, our leaders are nothing more than a 2-strand rope, albeit they are tapered!
The single-step process used by rope makers, which permits the release of the stored energy simultaneously with the simple twisting requires that the tippet end be twisted in the 'same' direction as the butt end, and at the same time. (Check out the numerous videos on YouTube on rope making.) We can, and some of us do, accomplish the very same thing by utilizing a ball bearing swivel to attach the thread to at the tippet end. The process also require the use of a "top" to keep the two legs separated during most of the process. Also, the butt ends of the legs are attached to the same two hooks throughout the entire process. As the legs are 'twisted, the swivel revolves in the same direction, releasing the stored energy, and resulting in simultaneous "furling", as the term is used by most. This has been thoroughly vetted on FURLEDLEADERS.CO.UK over the past couple of years.
Those of us there who have resolved most of the problems refer to the method employed by most (two legs twisted form different hooks and then switched to a common hook and twisted in the opposite direction to "furl") as the Traditional Method (TM), and the single-step method as the Rope Laying Technique (RLT). By using the RLT, one can get, theoretically at least, a maximum of 33% reduction, instead of the 10% traditionally used. Those of us who have 'shot' for the max have gotten as much as 30% reduction. HOWEVER, said leaders are almost as stiff as the board itself! We are in general agreement that 20-25% reduction yields a much firmer, or tighter, 'furl' and still produces a supple leader.
If you go to the literature on how the early 'furled' leaders were made using a Walton's Engine, you will find that they were made in a single step. The strands were hung from the "Engine" with a tension weight attached to the "tip" end. This weight would freely spin, releasing the 'stored energy' as the strands were being 'twisted', or 'furled' together. Hence, "twisting" and "furling", not only by definition, but also in actual practice, are synonymous.
Because the terminology in current use does infer a distinction between the two, to prevent massive confusion among the furling ranks, it is perhaps best that we do continue to use said terminology.
SMC, you are correct on how they are made. I cannot speak to the Offshore Swivel Knot, as this is the first time I have ever heard the term. The guys I have watched do a Bimini Twist first form a loop of mono around either their knee, or foot, and then begin to twist the two legs to form the terminal loop and create the 'twisted", or "furled" section, at issue in the original post for this particular thread. It is fascinating to watch a "Pro" do one!
Fishn50, you are absolutely correct.
Cheers!