I am not sure what you mean by "solved"? You are correct:
All Unix accounts used to execute R must be members of the Unix group that is the primary group of the Applications.RunAs user. Applications are not permitted to launch if the Unix account associated with the logged-in user does not have the proper group membership.
You can change the primary group or the default RunAs user from rstudio-connect to something else, but you must have all users who will execute code be a member of the same group. This requirement allows Connect to manage file and folder permissions appropriately.
If you have further questions, feel free to email firstname.lastname@example.org.