Answering my own question, here is one way to regenerate client secrets that will work same way as using the OAUTH package and preserve the secret in ORDS_METADATA.USER_ORDS_CLIENTS.

DECLARE

CURSOR get_clients IS
SELECT uoc.name,
uoc.description,
uoc.client_id,
uoc.client_secret,
USER oracle_user
FROM user_ords_clients uoc
ORDER BY NAME;

l_client_cred ords_types.t_client_credentials;
l_client_cred_null ords_types.t_client_credentials;

BEGIN

FOR a IN get_clients LOOP

l_client_cred := l_client_cred_null;


l_client_cred.client_key.name      := a.name;

-- l_client_cred.client_secret.secret := 'XaFhM690PA6cN1ffpkNx3Q..'; /* You can set the secret to specific value, NULL generates new value */

l_client_cred.client_secret.secret := NULL;  

l_client_cred.client_secret.stored := TRUE;


l_client_cred := ords_security.register_client_secret (

                   p_client_key      => l_client_cred.client_key,

                   p_client_secret   => l_client_cred.client_secret,

                   p_revoke_existing => TRUE,

                   p_revoke_sessions => TRUE ); 

/*
No Commit Required, only SLOT 1 is saved to DB
*/
SYS.DBMS_OUTPUT.PUT_LINE(a.oracle_user||
' Slot:' || l_client_cred.client_secret.slot||
' Issued On:' || l_client_cred.client_secret.issued_on||
' Name: '||a.name||
' Old Secret: '||a.client_secret||
' New Secret: '||l_client_cred.client_secret.secret);

END LOOP;

END;
/