I don't think that is exactly correct. Weld does not "stick" . The metal or pieces being joined together coalesce to form a joint, so if you use a high tensile strength bare wire rod there is no reason the pieces couldn't be joined.
True, he needs a gtaw welder and the right rod and shouldn't have any problems. I've made mini taps with a nut welded on top and have re-tapped some pretty knarly stainless threads before, no problem breaking the tap or weld.
