Well, the Mesh class extends AbstractMesh, which extends TransformNode. So, meshes are themselves transform nodes. Getting both the meshes and the other nodes from getChildTransformNodes is the expected behavior. It’s a more inclusive function.
getChildMeshes, on the other hand, returns exclusively the children who are meshes, excluding all other transform nodes. So in this case, it only returns PlaneMesh0 and PlaneMesh.
If you want to get only the non-mesh transform nodes, you could call:
getChildTransformNodes(false).filter(node => !(node instanceof BABYLON.AbstractMesh));```
This will filter the array, removing any node which is an instance of AbstractMesh.