My hatchery chicks also “bathe” in the shavings. Once when I dumped a bag of sand on the ground (to lay brick) and the pullets (my first little flock ever… four little hatchery chicks raised by me) immediately laid down into it and started flinging it everywhere. I think it’s more instinct than learned behavior. Maybe Shad’s comets and links have it partially bred out of them.
Edited to add, since I’ve been reading more if the discussion. Maybe it’s a combination of breeding and environment while developing. Can they never learn the behavior? Will they ever want to learn the behavior? This will be interesting to watch.
One if my current young hens, a hatchery black australorp, dust bathes just fine, but doesn’t shake the dust out, so post bath she walks around looking like she has a saggy diaper with dust all over her back.