List/TableColumn have default editCommit handlers, TreeView has none (see failing test below), introducing an inconsistency and breaking its spec:

"By default the TreeView edit commit handler is non-null with a default handler that attempts to overwrite the property value for the item in the currently-being-edited row."

Not having one might be the reason (wildly speculating ;) for
TreeCell to illegally take over the task in commitEdit and change the backing data (reported as JDK-8187309)

The fix for both is rather simple (and low risk, I think):

1. add a default handler like f.i.

        treeView.setOnEditCommit(e -> {
            TreeItem editItem = e.getTreeItem();
            editItem.setValue(e.getNewValue());
        });

2. remove interfering code in treeCell.commitEdit

// current code
        // update the item within this cell, so that it represents the new value
        // no, that's is wrong!
// if (treeItem != null) {
// treeItem.setValue(newValue);
// updateTreeItem(treeItem);
// updateItem(newValue, false);
// }

// replace with:
        updateItem(newValue, false);



The tests (pass for List/TableColumn, fail for Tree)

    /**
     * Test default edit handlers: expected none for start/cancel,
     * default that commits
     *
     * Here: Table
     */
    @ConditionalIgnore (condition = IgnoreTableEdit.class)
    @Test
    public void testTableEditHandler() {
        TableView<TableColumn> table = createEditableTable();
        new StageLoader(table);
        TableColumn control = table.getColumns().get(0);
        assertNull(control.getOnEditCancel());
        assertNull(control.getOnEditStart());
        assertNotNull("listView must have default commit handler", control.getOnEditCommit());
    }
    
    /**
     * Test default edit handlers: expected none for start/cancel,
     * default that commits
     *
     * Here: List
     */
    @ConditionalIgnore (condition = IgnoreListEdit.class)
    @Test
    public void testListEditHandler() {
        ListView<String> control = createEditableList();
        new StageLoader(control);
        assertNull(control.getOnEditCancel());
        assertNull(control.getOnEditStart());
        assertNotNull("listView must have default commit handler", control.getOnEditCommit());
    }
    
    /**
     * Test default edit handlers: expected none for start/cancel,
     * default that commits
     *
     * Here: Tree - fails, probably reason for cell taking over itself
     * (https://bugs.openjdk.java.net/browse/JDK-8187309)
     */
    @ConditionalIgnore (condition = IgnoreTreeEdit.class)
    @Test
    public void testTreeEditHandler() {
        TreeView<String> control = createEditableTree();
        new StageLoader(control);
        assertNull(control.getOnEditCancel());
        assertNull(control.getOnEditStart());
        assertNotNull("treeView must have default commit handler", control.getOnEditCommit());
    }