GPU backed securities also don't have that issue because they're far more transparent. The problem with mortgage backed securities is that nobody has the time to inspect the credit worthiness of each mortgage in a MBS, each creditor has hidden correlated risk (eg. if the whole economy tanks), and on top of all that trenching obfuscates the risk. Lenders therefore had to take the credit ratings on face value. It's hard to make the mistake with datecenter/gpu/anthropic debt.