Why is there a warning of changed password/email? Are those accounts hacked, or believed to be hacked, should we be cautious when dealing with those users?
exactly as you said, as warnings, they warn others about that account's security
the account may be hacked or the owner simply wants to change it for personal reasons
when change email and password reset/change notice shown at the same time
usually it's a sign of hacked account or sold/bought account
so you need to take precaution steps dealing with such account