Look up references also show up in Model Rights - New Objects. However the reference itself does not need any rights. If you do go to the object you get a screen which implies there are no roles in the project. Since there is no point in having this object appear in New Objects. Please hide these objects behind a pre filter.
Unfortunately, this idea has not received enough votes. Because we want to keep the focus on ideas that are in high demand in our Thinkwise Community, we are closing this idea.