Why are thread priority settings ignored in JBoss EAP on RHEL?

Issue

To increase the thread priority of the MDB threads that consumes messages from IBM MQ, I configure a custom thread factory in standalone-full.xml as follows. However, it does not work.

<subsystem xmlns="urn:jboss:domain:batch-jberet:2.0">
...
    <thread-pool name="batch">
        <max-threads count="10"/>
        <keepalive-time time="30" unit="seconds"/>
    </thread-pool>
    <thread-factory name="priority-factory" thread-name-pattern="mdb-thread-pool-%t" priority="10"/>   <<<===
</subsystem>
...
<subsystem xmlns="urn:jboss:domain:jca:5.0">
    <archive-validation enabled="true" fail-on-error="true" fail-on-warn="false"/>
    <bean-validation enabled="true"/>
    <default-workmanager>
        <short-running-threads>
            <core-threads count="100"/>
            <queue-length count="50"/>
            <max-threads count="100"/>
            <keepalive-time time="10" unit="seconds"/>
            <thread-factory name="priority-factory"/>   <<<===
        </short-running-threads>

The thread priority is set to the maximum of 10, but the PR and NI values remain the same as other threads.

$ top -b -n 1 -H -p <java-pid>
...
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
  65898 jboss-eap 20   0 3379480 830568  31064 S   0.0   3.4   0:00.00 java
  65899 jboss-eap 20   0 3379480 830568  31064 S   0.0   3.4   0:00.58 java
...
  66306 jboss-eap 20   0 3379480 830568  31064 S   0.0   3.4   0:00.01 mdb-thread-pool  <<<===
...

Also, If I try to modify the thread priority by calling java.lang.Thread#setPriority(int newPriority) in the application, the PR and NI values are not changed. Why are thread priority settings ignored in JBoss EAP applications on RHEL?