HIVE-2936 changes were made for warehouse table sub directories to inherit the permissions from parent directory. But this applies only to directories created by metastore.
When directories (in case of dynamic partitioning) or files are created from the MR job, it uses the default
But new partition files or directories created from the MR jobs don't inherit the permissions.
This means that even if the permissions have been granted on table directory for a group, the group will not have permissions on the new partitions.