What is the meaning of groups in the new access model, does it define access to the objects?
Groups are no longer the only way to control access in Workfront. In order for groups to receive access to an object, the object must be shared with the group. (Setting a group on the project or other objects will not automatically grant access to the users within that group.)
For information about sharing objects, see "Sharing Permissions on Objects."
Groups marked on templates, portfolios, and projects are used to identify with whom objects should be shared automatically at the time that the site is upgraded to the new access model.