After spending a while trying to figure out why my PopupMenus had a weird rectangle around them I found that PopupMenus call ResizableWindow::LookAndFeelMethods::drawResizableFrame.
Why? They aren’t resizable windows. And drawResizableFrame doesn’t take a parameter to the component that’s being drawn, so there is no way to determine if it’s actually a resizable window or a menu being drawn. Classes calling LnF methods from other classes seems wrong.