Such a behavior is currently not supported, sorry for any inconvenience caused.
You can remove the global setting and define UpdatePanelRenderMode per updated control only.
Another option is to wrap the control, which you want to have a block update panel, in a new block element (div). This additional block element will force a new line, eventhough the updated control's update panel will behave like an inline element.
All the best,
the Telerik team