Seen that pic many times, clean break in the weld no doubt about it although there's some confusion about that thinking back. The bike store (Evans) where she got it from said the break was due to excess stress on the whole assembly due to the hinge bolts becoming loose through lack of service. That was scoffed at the suggestion being they were just trying to shift the blame.
As I recall the lady had told them she always folded the bike away securely after use, but that's not what the store was on about. The point about the loose bolts is valid, although I wouldn't like to say if that was so in her case.
It's well known that if hinge bolts or any moving part of the assembly become even the tiny bit loose it throws more stress on the joint. That said you would not expect a sudden catastrophic failure to result unless the welds were not up to the mark.
I believe the new approach is as jur has pointed out, a stronger reinforced area around the hinge combined with a new more secure latch design, belt & braces as it were.