You have to recall the context in which those provisions were passed: coming out of the Civil War, you had both Union and Confederate bonds and other public deb

You have to recall the context in which those provisions were passed: coming out of the Civil War, you had both Union and Confederate bonds and other public debts used to finance the war. Amongst the other conditions upon which the rebellious states were re-admitted to political authority were the cancellation of Confederate debt (the Union was not going to pay for the wages of rebellion) and the guarantee of Union debt (so that Southern and Western states could not collude in Congress to prevent repayment of that debt), both of which were written into the Public Debt Clause. So the clause was absolutely meant to restrict the government's ability to repudiate debts other than those explicitly excluded, because you had a Republican Congress working to tie the hands of a potential future Democratic one. (N.B., I'm not exactly sure what you mean by "required to accept T-bills at face value" -- you can buy T-bills and TIPS on the secondary market at whatever price the market sets. If the US were to start defaulting on its debt, then that price ... would not be as stable as it has traditionally been.)