DEGREE parameter NOT working while gathering INDEX STATS

Hi

I tried to gather index stats using DBMS_STATS.GATHER_INDEX_STATS.
I used DEGREE parameter so that index stats are gathered in parallel. But when
I check the sql it runs as folowing:
SELECT /*+ no_parallel_index(t,"XX_BUILD_B17") dbms_stats cursor_sharing_exact use_weak_name_resl dynamic_sampling(0) no_monitoring no_expand index(t,"XXGDW_BUILD_B17") */

but gathering table stats using DEGREE parameter is working fine and is gathering stats in PARALLEL. DBMS_STATS.GATHER_TABLE_STATS.

The initialisation parameters are set as follows:

parallel_min_servers integer 0
parallel_max_servers integer 8
cpu_count integer 16
parallel_threads_per_cpu integer 2


Any thoughts on why index stats gathering is not happening in PARALLEL??

Thanks
Ram