splitbutton inside buttongroup behaving differently

Is it a bug ? or is there any workaround ? I want "SplitButton inside buttongroup" to behave the same as the other "Splitbutton"

Code:

Ext.create('Ext.data.Store', {    storeId:'employeeStore',
    fields:['firstname', 'lastname', 'seniority', 'dep', 'hired'],
    data:[
        {firstname:"Michael", lastname:"Scott"},
        {firstname:"Dwight", lastname:"Schrute"},
        {firstname:"Jim", lastname:"Halpert"},
        {firstname:"Kevin", lastname:"Malone"},
        {firstname:"Angela", lastname:"Martin"}
    ]
});


var contextMenu = Ext.create('Ext.menu.Menu', {
            id: 'accountListContextMenu',
            plain: true,
            items: [
                {
                    xtype: 'buttongroup',
                    title:'Actions',
                    columns: 1,
                    items: [
                        { text: 'Button1'},
                        { text: 'splitbutton', 
                         text: 'SplitButton Under ButtonGroup',
                         menuAlign: 'tl-br?',
                         menu: [
                              { text: 'Button3'}
                         ]
                        }
                    ]
                },
                        { text: 'splitbutton', 
                         text: 'SplitButton',
                         menuAlign: 'tl-br?',
                         menu: [
                              { text: 'Button3'}
                         ]
                        }
                    
            ]
        });


Ext.create('Ext.grid.Panel', {
    title: 'Action Column Demo',
    store: Ext.data.StoreManager.lookup('employeeStore'),
    columns: [
        {text: 'First Name',  dataIndex:'firstname'},
        {text: 'Last Name',  dataIndex:'lastname'},
        {
            xtype:'actioncolumn',
            width:50,
            items: [{
                icon: 'extjs/examples/shared/icons/fam/cog_edit.png',  // Use a URL in the icon config
                tooltip: 'Edit',
                handler: function(grid, view, rowIndex, cellIndex, item, e) {
                    contextMenu.showAt(item.getXY());
                }
            }]
        }
    ],
    width: 250,
    renderTo: Ext.getBody()
});

splitbutton inside buttongroup behaving differently