List command output not correct for super user, after grant command

Running local Cassandra with below config:

authenticator: PasswordAuthenticator
authorizer: CassandraAuthorizer
role_manager: CassandraRoleManager
network_authorizer: CassandraNetworkAuthorizer

Created a super user and then ran Grant select command on a keyspace. 

shaadmin1@cqlsh> CREATE USER 'shaadmin1c1' WITH PASSWORD 'shaadmin1c1' SUPERUSER;
shaadmin1@cqlsh:system_auth> grant select on testk1.t1 to shaadmin1c1;
shaadmin1@cqlsh:system_auth> alter role shaadmin1c1 with access to all datacenters;

After this, list permissions command showing only select permission for that role on the resource.

shaadmin1c1@cqlsh> list all permissions of shaadmin1c1;
role | username | resource | permission
----------------------------------------+-----------
shaadmin1c1 | shaadmin1c1 | <table testk1.t1> | SELECT

Row in role_permissions table:

role | resource | permissions
------------------------------------------------------------------------------------------
shaadmin1c1 | data/testk1/t1 | {'SELECT'}

But insert command by that role on the resource is successful because role is a super user

shaadmin1c1@cqlsh> insert into testk1.t1 (c1, c2) values ('a', 1);
shaadmin1c1@cqlsh> select * from testk1.t1 ;
c1 | c2
---+---
a | 1
(1 rows)

The problem is, output of list permissions command, which indicates only select permission on the resource, is misleading. I think list command need to be fixed to show all permissions super user has on the resource. Also grant command for a super user can be either a no-op or throw error, because the role already have requested permissions.

Documentation also misleading:

True automatically grants AUTHORIZE, CREATE and DROP permission on ALL ROLES.
Superusers can only manage roles by default. To manage other resources, you must grant the permission set to that resource. ** For example, to allow access management for all keyspaces: GRANT ALL PERMISSIONS ON ALL KEYSPACES TO }}{{{}role_name.