It's not confounding at all. It's making the point that internal motivation, according to the study, has no major factor in savings regret.

It says that understanding risk (as operationalized by understanding probability) has a larger effect.

But it is also saying that the more external impact someone has, the more they regret saving more -- in the United States but not Singapore.

The study is explicitly saying that internal motivation does not seem to matter. And the article is arguing the reason why.

Maybe I read the article too fast but I didn’t get that takeaway at all?

It’s basically just saying that the uninsured catastrophic event risk in America magnifies shock events.

E.g., if you have a major hospital visit in America you’re way more likely to regret not saving enough, but in Singapore there’s basically no effect since hospital stays don’t drain your savings account.

That’s what I also got from this article

Not just healthcare stuff, but also apparently Singaporeans tend to have a lower unemployment rate, so they be able to recover from stuff faster