By default, the front-end event type selector will show categories used by events in the current group/view.

You can override this to show specific categories on a per-group basis by adding this to your public.config.php file.

$_LW->CONFIG['CALENDAR_GROUP_CATEGORIES_TYPE']=[ // custom event types to display on group calendar(s)
        // Group ID => Array of event types
        1 => ['Category 1', 'Category 2'] 
];