Behaviour difference when creating a same object using project tree or context menu (Ctrl-Z / "annuler" function)

1st way to create a source

1. Open a new project and save the project
2. In the context menu, select "source" => a new point source is added in the modeler and in the project tree.
3. In the context menu select "Annuler" (or Ctrl-Z)"=> the point source is suppressed in the modeler but remains in the project tree. Save the project.
4. In the project tree, select the point source and suppress it => an error message occurs "l'élément n'a pas pu être supprimé"

As a user, I want to prevent the discrepency described above

2nd way to create a source

1. Open a new project and save the project
2. In the project tree, select "Sources>ajouter>nouvelle source" => a new point source is added in the modeler and the project tree.
3. In the context menu select "Annuler" (or Ctrl-Z)=> the command doesn't operate

A a user, I want to understand why two creation ways of a same object leads to different behaviours