To me, this is evidence that culturally, OpenAI is not operating with a "security mindset". In my experience this sort of thing is relatively uniform across a company's culture, so if user data is not being treated in a secure way, we might conclude that the AI development work itself is likewise not being treated with the thoughtfulness that engineering against threat actors requires.
Is your claim that e.g. Google or American Express would be equally likely as OpenAI to suffer this issue? If so I would definitely disagree. I would be extremely surprised to see this type of issue in e.g. gmail, and if it did occur I think it would be correctly perceived as a massive scandal. Yet Google is almost certainly using Redis for important use cases.
Part of having a security mindset is assuming that system components can fail (or be made to fail) in surprising ways and making sure that the overall system is resilient to those failures. This does not necessarily require, as you suggest, vetting every part of the system. After all, few organizations had vetted e.g. log4j, but that does not mean that all organizations were equally affected by the log4j vulnerability.
There are things that an organization could have done to prevent exposure to the problem with redis-py. Here are some examples:
I'm not really trying to claim that this stuff is simple or easy, or that a security mindset is common among tech startups; just that these are the sort of steps that a security-oriented company would take, and the fact that OpenAI apparently did not take such steps is (limited) evidence that OpenAI management is not operating with a security mindset.