If you don’t provide any apple-mobile-web-app-status-bar-style meta tag or if you provide one with the default value, the status bar will become black over black, so… just a black area on the screen (on some devices you will see just the battery icon). The user will not see the clock and all the other icons on the status bar.
From Safari on iOS 7 and HTML5: problems, changes and new APIs
Buoys doesn't have this meta tag and I'm experiencing the black box with battery issue on iOS7.