There's more to a UI layer than individual controls. Like spacing between them fitting platform conventions, and window resizing and text size needs them to coordinate.
To the contrary. Developing native apps is so painful that the average S&P500 company will treat it like a root canal. Given how meaningless native functionality is to them, they won't hesitate at the opportunity to serve you a shitty Electron app. Many of them are only successful because they didn't waste time writing native apps for each platform.