When you create a new pipeline from Blue Ocean this will always be created on Jenkins root even if you are in an organization that has a root ItemGroup different from Jenkins root.

https://github.com/jenkinsci/blueocean-plugin/blob/a986f24023c4192f94ce6fc5b28b2f4b1e7b1626/blueocean-pipeline-scm-api/src/main/java/io/jenkins/blueocean/scm/api/AbstractPipelineCreateRequest.java#L55