Dat staat netjes in het blog:
Announcing Windows 10 Insider Preview Build 21337 | Windows Insider Blog File Explorer Layout Update The default layout of File Explorer adds additional padding between elements. For users who prefer a more information-dense layout, there is a setting in View Options called “Use compact mode,” which will restore the classic layout of File Explorer. The UX for toggling this setting is not final. The level of padding is designed for better consistency with modern (XAML) experiences. This should also make it easier to work with File Explorer when using a touch screen.