Concurrent Statistic gathering not possible when connected via service?

i am trying to speed up the optimzer statistics gathering with the 'concurrency' option. This works fine, when the connection is established using the generic database service or direct connection to an instance,

but not, when connected through a service. Isn't it possible to spawn jobs when connected through a service?

Setup:

Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production

with  "Database Patch Set Update : 12.1.0.2.180116 (26925311)"

RAC

Parameter:

job_queue_processes: 100

resource_manager_plan:default_plan

parallel_force_local=true

select dbms_stats.get_prefs('CONCURRENT') from dual;

DBMS_STATS.GET_PREFS('CONCURRENT')

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ALL

service used:

]# srvctl config service -service job_class_xxx1-db xxxtest