I think it's pretty safe to say that there aren't many in the NHS who actually know all that much about breastfeeding.
Only the ones who actually care about it will inform themselves decently, given that it's not compulsory to learn about it in any great detail or keep yourself current, even as a midwife.
So when women are told to top up, it's usually because nobody knows how to support breastfeeding to continue and it's pretty easy to tell a woman to give her baby a bottle.
"Give him a bottle" - see, piece of piss to say it.
But, God, what a phrase to hear. I know, I heard it the day DS2 was born. And given that I breastfed my first for 17m, have supported other women to bf, am passionate about women getting the support they need to carry on and knew I could bf DS2, it was still a kick in the guts, I can tell you.