That is very true. It doesn’t mean it is ethical. It is quite common for people who are disabled, have a disease, or what not to be overly optimistic about success. Which caused them to be more willing to make poorly informed decisions.

Experiments like these are not inherently bad, but it is very easy to receive informed consent from the participant when they are not fully informed. That is why studies like this in academia require an ethics panel to review them.

To give an Elon musk’s track record with his various companies. I think it is completely reasonable to question the ethics of this study.