Testing your assertions there is a problem.
1. In a new app, setting UIStatusBarStyleLightContent in iOS 7 does nothing. The default style (black) still shows. This is because UIViewControllerBasedStatusBarAppearance is YES (default, if it is missing). To use this you would set UIViewControllerBasedStatusBarAppearance to NO. Doing this, you would get the white text throughout.
2. In a new app, the default text is already black, thus the Capture plugin shows fine.
We want to avoid depending on the value of UIViewControllerBasedStatusBarAppearance.The proper fix is to add a preferredStatusBarStyle override in your MainViewController.m to set the status bar style (when UIViewControllerBasedStatusBarAppearance is YES), and to also set it in viewWillAppear (for when UIViewControllerBasedStatusBarAppearance is NO). You could detect this setting as well to conditionally run your code. In this case for mobile-spec it would set it to UIStatusBarStyleDefault (or you could use the org.apache.cordova.statusbar plugin to control this by API, it uses the same concept).
With the assumptions above corrected, the pull request will now test ok (so you can see the statusbar change back from black to white when the plugin is dismissed)