This is an iOS specific issue. Apps which are downloaded from the Appstore are managed by Habyts, however, there are times you want to create a 'Shortcut' on your home screen.
'Shortcuts' look like an app on your home screen (as you see the icon), but it was 'shared' to your home screen and not downloaded. This happens when you select an option on a webpage associated with the icon.
Shortcuts cannot be managed by Habyts as they are not an app. One example would be the 'Financial Times'.
You can share games to your Home Screen - but these are not apps.
Some games can be downloaded from websites but do not require an internet connection. These games cannot be controlled by Habyts.
Note: Your child could 'get round' Study Time by playing web based games, unless you add the website to a banned list.