If there is an outbreak nearby or if the hatchery that shipped has an outbreak, they might need to locate your flock, unfortunately. HPAI is no laughing matter, either.
And I completely understand your reticence. I'd be alarmed, too.
I'd guess they need to know who has birds and where in case there are more outbreaks. I'm having flashbacks to the end outbreak in Southern California....
*shudder*