In terms of decision making, the classic Kahneman/Tversky studies seem to suggest exactly the opposite, that neutral to tempered-positive thinking leads to better decision making. However, I think the article says something else, something along the lines "if you see a bubbly optimist, he's likely to be an idiot", rather than imply that pessimistic people make better decisions (I only skimmed the original paper:
https://journals.sagepub.com/doi/10.1177/01461672231209400 so take it with a grain of salt). That matches my anecdotal experience and can be, in many ways, "verified" here on ET. Overconfidence is a prime form of excessive optimism and ET is overconfidence central.
In any case, my problem with the study is that it was done in the UK and does not correct for the cultural biases. It's hard to separate biological pessimism from ability to evaluate risk. It's probably even harder to separate biological optimism from the bullshit societal pressures. So my expectation would be that societies that foster a cynical, negative outlook on life (e.g. Russia) produce idiots who are cynical pessimists, while societies like the US and the UK (where every bit of media screams about meritocracy) produce optimistic, growth-mind-set idiots.