Resetting 11g paswords as part of upgrade to 12.2.0.1c

I am in the process of upgrading some 11.2.0.4g  databases to 12.2.0.1c and as part of the upgrade using dbua the 12.2.0.1 databases test for complex passwords.  Some of the schemas being upgraded have 10g 11g passwords flagged as needing revising.

I can set a password policy for new users/schemas and then force a password expiry  to make users reset their old passwords to the 12c format to resolve existing 'simple' passwords.  However when I tried this on a test schema the dba_users table still showed the password as being a 10g version so although the password had been reset (and met the complexity requirements) the dba_users table had not picked this up and still showed it as 10g.