The "User password changed by non-owner" and "user password changed" events are recorded when the unicodePWD attribute is changed. This unicodePWD attribute is not changed if the password is reset with the same exact password. This is the same of other attributes as well. For example, if you use ADSIEDIT to the update the telephone number but don't change the value, no event is recorded.
When a password is reset with the same password, the attribute of note that gets changed is pwdLastSet. Change Auditor does not use pwdLastSet to track password changes as it can generate false positives. If you want to be able to report on this type of password change, we suggest adding the pwdLastSet attribute as a monitored attribute. This would allow you to see when the attribute is updated as an indication that a change of some type was attempted.