Answer
Even in an SSO-authenticated environment, every IFS Applications user still has an underlying Oracle database account whose lifecycle can be queried via the standard Oracle dba_users view, which the application owner has default access to. Cross-reference the currently-inactive IFS users, from FND_USER where active = 'FALSE', against dba_users' own created, lock_date, and account_status columns to produce exactly this kind of active/inactive user list with creation and disable dates for SOX audit evidence, since account creation and lock dates are tracked at the underlying Oracle-account level even though FND_USER itself doesn't store them directly.