Yeah it seems there's a bit of asymmetry between a normal lender and the federal government here where as a normal lender you might not be able to lend enough to guarantee the debtor survives. Also what the gov decides to do may significantly influence the lender's behavior. If the lender thinks there's a chance the gov will bail them out, they would probably prefer that and not give a loan.

Whereas the federal government can write a check for $633.6 billion and be much more certain the debtors will survive and pay it back.