I think that calling something “feather tree” is often used by sellers either in ignorance or to indicate the size of an ornament. In the 20s and 30s, both Germany and Japan produced individual ornaments that were purchased one at a time by families to add to their collections. They also produced sets of ornaments specifically designed for the feather trees of the day. These were usually around 1-2” long ornaments. In today’s terms, they’d be called small or miniature. Of course, this size ornament is still produced today. The term feather tree is rightly applied to individual ornaments or the sets produced in that era.
There were many sets of miniature ornaments produced as decoration for packages both pre and post WWII. These most often were sets of tiny spheres. These are mistakenly identified as “feather tree”.