Layout panel does not show nodes in document order, doesn't always show newly attached nodes, and sometimes shows detached nodes because it doesn't observer NodeInserted/NodeRemoved, and just appends new layout containers to the end of the list. This is an issue for sites that dynamically add/remove elements from the DOM (including Web Inspector itself) because element order is not stable and detached nodes won't be able to have their overlays turned on in the backend anyways.