I mean , yes .. there is some truth to it .. but over simplificatiion blows my mind .. first of all we need to understand that the people buying sovereign debt are not stupid .. and they have thousands of choices to invest their money it rather than simple T-bills ..
Discussion
The world needs dollars because important resources, such as oil, are settled in dollars. Most debts are settled in dollars. When there is a market crash, global demand for dollars goes through the roof, called a rush to liquidity, because people sell assets to acquire dollars to cover margin calls.