Calling these divers reckless is inappropriate. I happen to know many on your dive. They are NOT reckless divers. They can dive this dive on steel 100s without redunancy safely if they so wish. I have done it myself safely many times. It's all about gas consumption and nitrogen loading. If you follow the rules there is no issue. If one diver reached 500 psi during a 10 minute deco stop, well that may or may not be an issue. He or she needs to speak to his/her maker in the end.
This is an age old issue of safe gas management practices.
The question isn't about 500psi or tank size or computer usage, it's about "if his buddy had a total regulator failure at their maximum penetration point at HITW, would the other buddy had enough gas to get them both to the surface, without missing any decompression obligations?" If yes, then there is no problem. If no, then there is a problem, and you have to decide if you should say anything.
At a minimum, you might ask the diver about his gas management. If it seems reckless, you might mention it to the captain at some point. If I were a boat captain, I'd want to know about the liability of various divers, I think. I've never been a boat captain though, so I might be wrong. But it never hurts to start by asking a "reckless" diver about their dive, to make sure you don't jump to conclusions.