It’s in continuing the topic about the spread. If you had the decision to keep this instrument in your portfolio, you could make some money by trading the spread. These state issues have equal coupon and time of its payment. But this is not so important and can be used for others.
When the market falls, the absolute spread between their quotes increases, and the relative yield decreases.
This is reason why percentage curve has inversion and has arched in other direction.
Moving from one bond issue to another during a fall, you solve two problems: taxes when you sell at a loss and free money when you come back.