I think it says something different. The article you referenced says "it's largely leaving backyard flocks unscathed". And that sentence links to another article by USAToday that says "bird flu outbreak mostlyspares backyard chickens".
I just lost a bird and I am not sure why. There were no symptoms until just at the end, like, within an hour. On Tuesday she was fine -- laid an egg in the morning. On Wednesday she did not lay an egg. That is unusual for her but it occasionally happens. Thursday I noticed something wrong around 9:30am. She was laying down with her head on the ground, eyes closed and panting. I picked her up and put her in the coup. She just stood in one place, not moving, with her eyes closed, panting. By 10am she was dead. She showed none of the other symptoms of bird flu. Whatever killed her was really fast. I cannot say it was bird flu, and I cannot rule it out, either. I can only watch our other 5 birds and see if they stay ok.
The worst part -- that last egg, the one she laid on Tuesday -- it was used to make mayonnaise. I noticed the white of the egg was more watery than normal but did not think much about it. That mayo was used in 2 sandwiches which were consumer before the bird died. Cooked poultry does not transmit bird flu. Mayo is made with raw egg. So now we wait.