I went to lengths trying to get info of this bikes provenance, the guy has no idea what he is selling/sold...lets say it certainly is not a pierobon frame, and from closer inspection is pretty tatty. He reckoned his mate who works for ducati in Italy built it...ummmm ok!
Heres a supermoto 550 frame going together and its tig welded. Maybe they only started tig welding late 1990s .