Correct, If you change your password on the 4images side, it will change the password on the SMF side.
BUT, if you change your password on the SMF side, it WILL NOT change the password on the 4images side.
That is why in my mod, I tried to remove all attempts to login/change password from the SMF side so you would be handling alll that from the 4images side.
Not a clean cut solution but it works in some environments.