It's pretty much 1/3 the depth which is suspiciously close to a 3x safety factor which is what I've always heard engineers use. They certainly seemed cavalier with safety, so it wouldn't surprise me if they reasoned about it in that way.
It’s all relative. Good engineering doesn’t mean higher number.
No one knows what the FOS for this sub was. Given the information from the CEO, things like that were just slowing down innovation!
EDIT: Not all rockets, just using an example.