Meh, the article doesn't mention recovery rates. If a loan defaults it's not usual you are getting 0 back. Typically 30-40% is the assumed rate. That means if all the loans default then the top 30% of tranches shouldn't take a loss.
So now consider, most of the underlying loans have to default and the recovery rate has to be below battle tested assumptions before the top tiers get risky. This is very very unlikely to happen given the Fed and the US Govt. have done so much and are committed to do more to stave off a severe depression / recession. It's more like people were killing it buying the safer parts at distressed prices as over leveraged funds shed them on the back of margin calls in March.
So now consider, most of the underlying loans have to default and the recovery rate has to be below battle tested assumptions before the top tiers get risky. This is very very unlikely to happen given the Fed and the US Govt. have done so much and are committed to do more to stave off a severe depression / recession. It's more like people were killing it buying the safer parts at distressed prices as over leveraged funds shed them on the back of margin calls in March.