This is where we will agree to disagree. If something has a safety factor of 5:1, lets say the expected load is 100 lbs on the cruiser, then they'll build it to 500 lbs giving it the 5:1 ratio.
If the race boat's expected load is 1000 lbs they'll build it to 2.0x that. 2,000 lbs. This doesn't make the race boat stronger just b/c it can stand higher loads. It's REQUIRED to withstand higher loads b/c it generates them.
I understand what you say and I have no problem with different opinions but I don't think you are looking at itthe right way:
5:1 ratio is a very good ratio even for a cruising boat, but let's accept that as the right figure for expensive boats. But the 1:2 ratio is completely out for a boat able to do a non stop circumnavigation in high latitudes. We have seen that the only mandatory ratio, 1:4.1 was raised to 1:5. I believe most of the boats will be built with not less than a 1:3 ratio, probably between 3 and 4 in most cases.
This ratio on a Imoca boat regard the highest loads the boat experience (the same with the cruising boat) that in this case is sailing between 20 and 30K and sailing on high latitudes were waves can reach many times over 30ft.
The difference in loads regarding speed is not a progressive one but an exponential one. The same boat sailing at 30K is not sustaining 50% more stress than at 20k the same way a boat sailing at 10k is not sustaining half the stress than he takes at 20K but much less. Even a difference of 5 or 6 K can double the loads on the hull and keel.
I now this but I cannot tell you exact figures. For the sake of discussion let's assume that at 20k the same hull is experiencing 3 times more stress than sailing at 10k (I would say that factor is much bigger).
So in this case let's consider your 1000lbs load that taking into consideration the 5 factor used for a cruising boat will translate in a breaking load of 5000lbs.
The same load on a racing boat wit a 3 factor would translate in 3000lbs but considering that the boat is built to sustain the conditions on high latitude and to be sailed at 3 times the speed of the cruising boat (between 20 and 30K) we would have to consider another factor due to the needs of sustaining these conditions, that corresponds to the differences in magnitude of the maximum loads the two different boats will sustain. Let's take the 3 factor as that difference in magnitude even if I consider that in reality it is a bigger one:
Than we have for the Imoca: 3000lbs .3 = 9000 lbs of breaking load while the top cruising boat will have 5000lbs.
This does not mean that if the top cruising boat and the Imoca are sailed to the worse loading conditions they are designed to sustain, meaning the cruising boat on average latitudes and at 10/11k and the Imoca on high latitudes at 26/30k, the cruising boat will not be more reliable, quite the contrary, but will mean also that if the racing boat is sailed at half of its potential (in what regards stress and speed), it will be more reliable than the cruising boat.
Those were the conditions that, according with what Stamm said, the boat was being sailed when it broke. The boat was not being raced but sailed in a safety mode, being on autopilot with them inside.