To reproduce

• dbl-click on a leaf page (one w/o children) in website
• w/o doing any change, go back to the tree view
• you'll see that the modification date has been updated and the page status is now modified.
  The issue seems to affect only leaf nodes. It was introduced in 5.1.1 (I checked 5.1 and that is OK)

A little debugging showed that the issue seems to be in info.magnolia.jcr.wrapper.LastUpdateNodeWrapper.addNode(String, String) starting at line #210
where the code reads

if (RepositoryConstants.WEBSITE.equals(this.getSession().getWorkspace().getName()) && NodeTypes.Page.NAME.equals(primaryNodeTypeName)) {
            // no LUD update on adding subpages
        } else {
            this.updateLastModified();
        }

while primaryNodeTypeName is mgnl:area (a non optional area is auto created). The reason why this happens only on leaf nodes is probably that pages above in the hierarchy are bootstrapped with those areas already created.