A cold weld (in this case) is one that doesn't have a lot of heat soak into the surrounding metal. The heat soak will anneal the tempered(heat treated) frame and basically revert it to mild steel making it weak. Where the weaker metal transitions to the stronger metal cracks can form due the weak being able to flex against the strong. Essentially it probably means our frames were TIG wleded instead of the more popular production MIG welding. TIG can be more precisely controlled and effects a smaller area of metal, but is far more time consuming than MIG.