The core idea
Purchasing managers' surveys can move bonds because they provide relatively timely information about business activity, orders, employment and prices.
What is happening underneath
A material surprise can change expectations before official output data are released.
How investors should read it
Bond investors often compare growth and price components rather than relying only on the headline index.
The same market move can carry different information depending on which maturity, issuer and risk premium is changing. Read the question together with the underlying concepts rather than treating one price move as a universal signal.