Database, workshop, external tool and assignment are not shown by users on frontpage by default because they doesn't have any permission to view it (because frontpage role is being used).
Those activities can be created but then if you login as student (or check from the app) they are not shown in fact I found in data activity:
'mod/data:viewentry' => array([...]
'frontpage' => CAP_ALLOW, // needed for databases on the frontpage
but there are many other capabilities needed.
It has always been like that but it does not make any sense to have this exceptions.