When I place a creole tree inside of a component in a component diagram, I only get one level regardless of how many levels the tree has. In other words, all nodes are flattened to the first level.
http://www.plantuml.com/plantuml/uml/SoWkIImgAStDuOfspiyjoCzBpIjHS8nLI2nMSEGgIaqkISnBpqbLK7BAhr1mKbAevb80WcIuIYU5QA081FYabgNcA1Z2-JNnK26ZHA0OXgXneW9MuIIieiaWKKnn4-n6fs1n17PpKy6YiLorN8uAkdOAJbmEgNafmE000000
See this example, where everything under Level 1 is the same, rather than hierarchical.