I skimmed through that PDF and didnt see anything specifically mentioning fully translucent feathers like above. The only mention of translucency is small lines across the feather
Figure 3. Stress marks in the feather of a Blue and Gold
macaw (Ara ararauna). These translucent lines in the vane
of a feather are generally oriented perpendicular to the shaft
and may develop in a growing feather during a transient
period of stress or disease.
And if it was PBFD I think we would for sure know at this point because a lot of our in-store birds are heavily molting and growing feathers back normally including birds she was caged near. Not gonna rule it out of course but my thoughts are more along the lines of either a feather that just didn't develop correctly for some reason or maybe malnutrition? Calcium deficiencies? I can bring it up with my boss and see if she can bring Harlee in for a test.
edit: appears the post I was replying to was deleted so this post is gonna be somewhat out of context xD