All Smartsheet objects can be shared to a group, apart from Calendar app. Calendar app asks you to share directly with an individual user or share the source sheet with a group.
One of the significant benefits of Works Apps & Dynamic view is that you do not need to share the source sheet thus making the user experience cleaner and more bespoke. Can Calendar app not be configured to recognise existing user groups in the same way as Dynamic view & Work Apps? Having to add/remove an individual user to a view (when you have 100's of users and 12's of views) creates a lot of additional administration