Why is Messaging Cluster able to start and form cluster with random usernames in MRG 2.0 ?

Issue

Cluster is able to start and form a cluster with random usernames.

Broker 1

cluster-mechanism=PLAIN
cluster-username=adminuser1
cluster-password=admin45
cluster-name=Rrajaram
realm=QPID
auth=yes

Broker 2

port=5871
cluster-mechanism=PLAIN
cluster-username=adminuser
cluster-password=admin4512
cluster-name=Rrajaram
realm=QPID
auth=yes

These users are not present in the SASL database

sasldblistusers2 -f /var/lib/qpidd/qpidd.sasldb
admin@QPID: userPassword

Cluster is able to start and form a cluster with random usernames.