If we believed that was true, we wouldn't invest. At retirement, a 100% chance of $X is worth much more than a 50% chance of $2X and a 50% chance of $0.
The average person has a worse understanding of investments than does ChatGPT, including with regard to logical consistency and following the implications of what they say they believe. This is also why so many treat lotteries and pyramid schemes as "good investments".
Even one step up from that, my dad's advice to me was: "Invest in Lloyds bank, if they go under we have bigger problems". We had bigger problems.
(To riff off what some ancient dead Greek philosopher said, the only reason I can meaningfully regard myself as better informed than most, is that I am aware of how little I know).
I think that is how normal people (is the term "unsophisticated investors" or does that mean something importantly different?) view sock market investments — sure, it says your investment may go down as well as up, but how many normal people doing investments act like that's true?