Our African Gray parrots do the same thing ;I think it is a greeting as much as anything. However  , I do break open the sheaths on new neck feathers . In the wild, birds will open these new feathers for each other. You can feel the smooth shafts , pinching them between finger nails releases the new feather. The bird will pull away and may bite if you get a shaft that is not ready. We ,or the vets, have never seen a problem on these birds.

Our African Gray parrots do the same thing; I think it is a greeting as much as anything. However, I do break open the sheaths on new neck feathers . In the wild, birds will open these new feathers for each other. You can feel the smooth shafts , pinching them between fingernails releases the new feather. The bird will pull away and may bite if you get a shaft that is not ready. Both we and the vets have never seen a problem on these birds.