Those are two different things. The first is record based, the second message is object based.
Revert field contents is displayed when a validation condition fails, IE entering text into a date field where date format is required, or entering in more than 10 numbers into a field that requires exactly ten digits. In this case, the validation is run BEFORE you exit the active field and try to commit the record.
This trigger (OnRecordRevert / OnRecordCommit) is geared towards a commit to the entire record, which would only happen AFTER the OnObjectValidate trigger has already passed valid.
Order of operation is very important to consider. It's covered on the certification tests too. Read up on this article a bit more to understand the order:
got it.. thanks for clearing it up