Not sure if I understand right from slack conversation. So if we using baseDn with unknown attributes like 'ds' then it should be failed.

Steps to reproduce (v. 7.0.0):

1. Download and install DS

   dpkg -i DS_7.0.0-M2020-10.3-1_all.deb

2. Setup DS with ds-user-data profile and set the profile baseDn to 'ds=example,dc=com' then start DS

   ./opendj/setup --serverId first-ds --deploymentKeyPassword password --rootUserDn uid=admin --rootUserPassword password --monitorUserPassword password --hostname localhost --ldapPort 1389 --ldapsPort 1636 --httpsPort 8443 --adminConnectorPort 4444 --profile ds-user-data --set ds-user-data/baseDn:ds=example,dc=com --acceptLicense
   
   ...
   Validating parameters..... Done
   Configuring certificates....... Done
   Store the following deployment key in a safe place and re-use it when
   configuring other servers in the topology:
   XYZ
   Configuring server..... Done
   Configuring profile DS user data store....... Done
   To see basic server status and configuration, you can launch
   /opt/opendj/bin/status
   

3. Try ldapsearch

   ./opendj/bin/ldapsearch -h localhost -p 1636 --useSsl -X -D uid=admin -w password -b "ds=example,dc=com" "(&)" dn
   dn: ds=example,dc=com
   

Second strange thing is when we setup old version with this invalid baseDn when after upgrade to version 7.0.0 so data disappears.
Steps to reproduce (from 5.5.3 to 7.0.0)

1. Download and install DS 5.5.3

   dpkg -i DS_5.5.3-1_all.deb

2. Setup DS with sampleData

   ./opendj/setup --rootUserDn uid=admin --rootUserPassword password --hostname localhost --ldapPort 1389 --enableStartTls --ldapsPort 1636 --httpsPort 8443 --adminConnectorPort 4444 --baseDn ds=example,dc=com --sampleData 200  --acceptLicense
   
   Validating parameters..... Done
   Configuring certificates.....WARNING: An illegal reflective access operation has occurred
   WARNING: Illegal reflective access by org.opends.server.util.Platform$PlatformIMPL (file:/opt/opendj/lib/opendj.jar) to constructor sun.security.tools.keytool.CertAndKeyGen(java.lang.String,java.lang.String)
   WARNING: Please consider reporting this to the maintainers of org.opends.server.util.Platform$PlatformIMPL
   WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
   WARNING: All illegal access operations will be denied in a future release
    Done
   Configuring server..... Done
   Importing automatically-generated data (200 entries)....... Done
   Starting directory server............ Done
   
   To see basic server status and configuration, you can launch
   /opt/opendj/bin/status

3. Run ldapsearch

   ./opendj/bin/ldapsearch -h localhost -p 1389 -D uid=admin -w password -b "ds=example,dc=com" "(&)" dn
   
   dn: ds=example,dc=com
   
   dn: ou=People,ds=example,dc=com
   
   dn: uid=user.0,ou=People,ds=example,dc=com
   ...
   

4. Upgrade DS to 7.0.0 version

   sudo dpkg -i DS_7.0.0-M2020-10.3-1_all.deb

5. Check that DS was updated
6. Run the same ldapsearch (or same but change to ldaps port + useSsl option)

   ./opendj/bin/ldapsearch -h localhost -p 1389 -D uid=admin -w password -b "ds=example,dc=com" "(&)" dn
   # The LDAP search request failed: 32 (No Such Entry)
   # Additional Information:  The search base entry 'ds=example,dc=com' does not exist

Looks strange that DS accept this baseDN during setup but during upgrade with data with this baseDn are disappears.

Note: It does not happens only with 'ds=example,dc=com', I tried with more invalid - like 'dcou=com' with same result.