I had Cinelli 1R break on me a the usual place. Scared the crap out of me, but fortunately I was going about zero miles an hour. I rode it home. I don't want to imagine having a steerer break

My impression is that steerers all have cut threads. BITD, Trek had a steerer threading machine. You can see it in the picture of Dick Nolan and Mike Appel from the vintage Trek brochure.