There is a difference between "spot welding" and "resistance welding" as a process, even though they both rely on resistance heating.
Spot welding is literally what it says, creating little spot welds joining two overlapping pieces of metal. Spot welding may be used, for example, for attaching metal tabs to batteries.
Bandsaw blades are joined by resistance welding, where the two ends of the blade are butted up together and the whole blade is heated to melting point by passing a current through it. The weld is not confined to a small spot, but covers the whole length of the join.