No, that is the recommendation according to my HV (although my HV said that her personal recommendation is that as long as baby had a varied diet she didn't think it was necessary).
Apparently because formula is fortified with iron and other vitamins, whereas breastmilk is supposedly low (HOWEVER, breastmilk is designed for babies, so I can't see how it would not be the most beneficial! Think they're talking out of their arse, personally). Then again, if you're giving baby cereal (like baby rice) that's fortified with vits & iron too, so I wouldn't worry...