I rerun the test and now I noticed the following message:
"10/02/23 22:23:05 WARN mapred.DeprecatedQueueConfigurationParser: Configuring "mapred.queue.names" in mapred-site.xml or hadoop-site.xml is deprecated. Configure queue hierarchy in mapred-queues.xml".
Looking back to reconstruct our thoughts - I believe we probably ignored this message, which is among the many similar warnings about deprecated keys in the conf file. Since we do put a properly formatted mapred-queues.xml in the classpath, we thought mapred-queues.xml should be loaded. I think the warning message could be more explicit, e.g. "Confiure queue hierarchy in mapred-queues.xml and remove "mapred.queue.names" from mapred-site.xml". Or "mapred-queues.xml will be ignored since you have "mapred.queue.names" defined in mapred-site.xml".