Exactly the same splicing method was described in a german DIY book, "Knaurs Handwerksbuch", printed in 1958. This was a suggestion how to splice 2 extension cords in order to get 1 long one. Only it suggested using EITHER friction tape OR rubber tube. Rubber tape never really caught here, we went straight from cloth friction tape to PVC tape.
Could this apply for small stranded conductors (say #18 in an appliance) or is it just intended for high-power, large diameter cables?
I once saw someone's website showing how to splice a piece of auto wire (usually #18 or #16). You butted the two ends together and then wrapped a single strand of wire (from a scrap piece of lamp cord). Then the joint was soldered and a piece of heatshrink tubing slipped over the joint.
I may try it ... just for kicks ... on some hook-up wire I have for electronic projects and speaker wire.