For me once it redownloaded and the next time xcode just refused to work and didn't even redownload. So it seems it has changed (or for me). The problem is, with Apple you don't even know it was done hostilely or it was just their, now well-establisehd, software incompetence. Because in their case both are aplenty.
In Xcode, go to Window > Devices and Simulators in the menu bar (or press Shift+Cmd+2), then select the Simulators tab in the sidebar to open the list of simulators. Here you can select and delete simulators.
