Docs say it should.

Works:
Code:
Ext.Anim.run(Ext.getBody(), 'fade', {
                        out         : true,
                        duration    : 500,

                        autoClear   : false
                    });
Doesn't work
Code:
Ext.Anim.run(document.body, 'fade', {
                        out         : true,
                        duration    : 500,

                        autoClear   : false
                    });