Where the zero-coupon analogy stops

What does a Treasury zero have that a PT does not?

• A price below face before maturity
• An issuer that owes the face amount on the maturity date
• A market where it can be sold early

A PT matures while its token trades well below the exchange rate. You need ETH today. Which value turns into cash?

• The exchange-rate value, because that is what the PT promised
• The market price you can sell the token for
• Whichever is higher