SPLUNK_DEPLOYMENT_SERVER Environment variable is not used/considered

Splunk Version: Latest (9.0.0)
As mentioned here: https://splunk.github.io/docker-splunk/EXAMPLES.html
the SPLUNK_DEPLOYMENT_SERVER variable is not used or considered in the startup
Event the entrypoint.sh is not listing this.
after pulling splunk latest we create and run as follows:

docker run --name splunk-uf -h $HOSTNAME -e "SPLUNK_PASSWORD=MySecurePassword" -e "SPLUNK_START_ARGS=--accept-license" -e "SPLUNK_DEPLOYMENT_SERVER=192.168.12.3:8089" -d splunk/splunk:latest
After a while this is the command what we run:
docker exec -u root splunk-uf /opt/splunk/bin/splunk show deploy-poll -auth "admin:MySecurePassword" WARNING: Server Certificate Hostname Validation is disabled. Please see server.conf/[sslConfig]/cliVerifyServerName for details. Deployment Server URI is not set.

Start by reading entrypoint.sh and the deployment-server example linked in the issue to trace how startup environment variables are handled. Reproduce the Docker command, then verify with splunk show deploy-poll that SPLUNK_DEPLOYMENT_SERVER is configured and reported as the deployment server.