‘realm join –client-software sssd’ on centos-7 joins two realms (one with sssd and one with winbind)

On clean installed centos-7 host:

realm join -U foo --client-software sssd AD.EXAMPLE.COM

After running realm list output looks initially like this:

AD.EXAMPLE.COM
  type: kerberos
  realm-name: AD.EXAMPLE.COM
  domain-name: ad.example.com
  configured: kerberos-member
  server-software: active-directory
  client-software: sssd
  required-package: oddjob
  required-package: oddjob-mkhomedir
  required-package: sssd
  required-package: adcli
  required-package: samba-common
  login-formats: %U@ad.example.com
  login-policy: allow-realm-logins

Showing me that I joined an active directory with sssd as I had intended.

Later on (not sure what triggers or it … a system reboot guarantees it, but other things seem to as well — maybe a samba restart?), the realm list output changes to this

ad.example.com
  type: kerberos
  realm-name: AD.EXAMPLE.COM
  domain-name: ad.example.com
  configured: kerberos-member
  server-software: active-directory
  client-software: winbind
  required-package: oddjob-mkhomedir
  required-package: oddjob
  required-package: samba-winbind-clients
  required-package: samba-winbind
  required-package: samba-common
  login-formats: AD\%U
  login-policy: allow-any-login
AD.EXAMPLE.COM
  type: kerberos
  realm-name: AD.EXAMPLE.COM
  domain-name: ad.example.com
  configured: kerberos-member
  server-software: active-directory
  client-software: sssd
  required-package: oddjob
  required-package: oddjob-mkhomedir
  required-package: sssd
  required-package: adcli
  required-package: samba-common
  login-formats: %U@ad.example.com
  login-policy: allow-realm-logins

How did I become joined to the same domain via both mechanisms? Is there a way I can NOT have this happen? Or is this somehow needed behavior?