It is also possible the Jem'Hadar were full of it in their titular episode, attributing all the MIA cases they found in UFP and Bajoran archives to their own heroic acts of slaughter, when in fact they never laid a polaron beam on USS Maryland which returned safe and sound a few weeks later.
Possibly they also took credit for the fact that local poisonous flora had killed all the people of New Bajor?
Starfleet does continue to enjoy some limited access to Gamma after the Jem'Hadar make this claim. But perhaps they believe in the propaganda and never go to check on the colony?
Timo Saloniemi