In my domain i use 'winbind use default domain = yes'.

I've also enabled ''offline logons'' following the samba wiki, and i've noted that (in 'smbcontrol winbind offline' mode):

 root@vdmsv1:~# wbinfo -K LNFFVG\\gaio
 Enter LNFFVG\gaio's password:
 plaintext kerberos password authentication for [LNFFVG\gaio] succeeded (requesting cctype: FILE)
 user_flgs: NETLOGON_CACHED_ACCOUNT
 credentials were put in: FILE:/tmp/krb5cc_0

 root@vdmsv1:~# wbinfo -K gaio
 Enter gaio's password:
 plaintext kerberos password authentication for [gaio] succeeded (requesting cctype: FILE)
 credentials were put in: FILE:/tmp/krb5cc_0

eg, only using the domainful user ('LNFFVG\gaio') wbinfo reply adding 'user_flgs: NETLOGON_CACHED_ACCOUNT', using the short form no.

I've done some auth test, and cached credentials works as expected, simply wbinfo reply in different way.

Thanks.