Basically, when the Element Picker box is hovering over the outline area, clicking in the hovering box selects the elements in the layout below. It’s as if the hovering box is transparent to clicks (though it picks up the clicks itself too, so a kind of double action occurs where the Element might be selected in the hovering box, and the layer / element in the Outline also gets selected.
A bit odd! Hope that makes sense. Happy to elaborate if it doesn’t, or get a video clip of what’s happening