PhoenixAccessController should use AccessChecker instead of AccessControlClient for permission checks.
In HBase, every RegionServer's AccessController maintains a local cache of permissions. At startup time they are initialized from the ACL table. Whenever the ACL table is changed (via grant or revoke) the AC on the ACL table "broadcasts" the change via zookeeper, which updates the cache. This is performed and managed by TableAuthManager but is exposed as API by AccessChecker. AccessChecker is the result of a refactor that was committed as far back as branch-1.4 I believe.
Phoenix implements its own access controller and is using the client API AccessControlClient instead. AccessControlClient does not cache nor use the ZK-based cache update mechanism, because it is designed for client side use.
The use of AccessControlClient instead of AccessChecker is not scalable. Every permissions check will trigger a remote RPC to the ACL table, which is generally going to be a single region hosted on a single RegionServer.