of course, before carbon frames came along, no steel, titanium or aluminium frame had ever broken....
Under front impact a 531 frame would tend to buckle at the top tube and down tube near the steerer tube. Forks are so strong they are not the first to go. The point is that steel does not completely snap.
I had a 531 bike hit side on by a van. The frame appeared undamaged but what I and the LBS failed to spot was that the down tube had a tiny impact mark and was minutely bent.
The bike was refitted and put back on the road. Over a year later the frame started to creak and was found to have a crack going 2/3 round the down tube beside the band-on gear lever. Being 25 miles from home on the N York moors, I decide to ride it home very carefully and it made the journey without the crack becoming worse.
Eventually the down tube was replaced by a 1st rate builder and I continued to ride the bike* until it was stolen a couple of years later.
*incl a couple of 50+ mph descents