No, Romney refuted a fact and he was wrong. For the Moderator to interject to confirm or deny a fact is necessary to keep the debate from devolving into continuous counter-assertions. (Yes I did!! No you didn't!!)
If you are looking for the moderator to keep them factual then the debates would last 10 hours and nothing would be accomplished.
To me that is an excuses that doesn't cut it. If it did devolve to a YES I did! No You Didn't! thing then she interupts and gets them back on target but she does not refute them on any facts or policy.
If you disagree then that is fine. To me she messed up and any attempt to justify it is pure ********.