Honestly, I just read a few other articles about Bridgewater Associates, and even though it seems cult-like, I think the principles probably help prevent group-think. For instance, the second most important goal is no talking about people behind their back. If any of the companies I worked at had this rule, I'd think they were trying to make people toe the company line. However, this rule actually supports the first rule, encouraging transparency, really well.
For instance, have you ever been in a situation where you are doing something wrong, only to find out later that people noticed but nobody told you? The consequences aren't that bad if your tie is on backward, but I've made expensive mistakes because nobody spoke up, and I've been in organizations where there was such a negative stigma around "confrontation" that mistakes happened all the time and gossip was rampant.
Studies have shown that groups that are told they much come to a consensus make worse decisions than groups that are encouraged to disagree. The difference can be pretty marginal, but a marginal difference in return can result in huge gains or huge losses when you are dealing with markets.
It definitely reflects poorly on a company when stories come out about employees crying in the bathroom. One can only imagine the psychological horrors that must go on at such a company! However, in my experience, there is a certain kind of person whose entire self-worth is based on their success. They are typically very high achieving, but failure is an anathema to them. They try to avoid failure at all costs. They end up under incredible strain, because failure is inevitable.
I've known a lot of people like this. There was one person I knew who was so stressed when she didn't know a question on an exam that she ended up vomiting all over the test. Another time, I caused a woman to cry in Model U.N. by vetoing her Security Council resolution as the Russian Federation. If you know anything about Russia and the Security Council, a veto is not exactly an uncommon measure from them. However, it meant we ended 5 days of debate on an issue without passing a resolution. She took the veto as hard as if I had vetoed a judgement of her character. She was a grad student at a prestigious school, so I'd say she had to have been in her mid-20s, which is definitely old enough to be working at a high-powered investment firm.
I personally think I'd like that environment. I do really well when I have a lot of autonomy, and I don't need much supervision to work. I hate it when people don't criticize my work. It just makes me paranoid; I know I'm not perfect, and I know there are flaws. I learn from every critique and failure. I know a lot of people that would have a mental breakdown in that environment though. It's hard to tell who those people are ahead of time though, because they are such high-achieving individuals, and their anxiety about failure is basically invisible.
So, to answer your question more seriously, I think their continued success is evidence that they must comfortable challenging their beliefs. However, I do think a holy book full of principles seems a little cult-like, especially in light of the fact that they are building an AI clone of their CEO.