In order for a group to show up in the Manage Groups part of Site Info, it must have the property:
This is defined in:
site-manage-util/util/src/java/org/sakaiproject/site/util/SiteConstants.java: public static final String GROUP_PROP_WSETUP_CREATED = "group_prop_wsetup_created";
Therefore, other tools that want to create groups with this property must either take a chance that the property won't change and hard code it themselves, or use the constant from the site manage utils, creating a hard dependency.
Ideally, this property would be moved to the kernel.