Just a thought, but the word 'weaning' has more than one meaning. I wonder if
this might be relevant.
Some people use 'weaning' to mean starting solids, or taking anything different
from milk.
It also can mean the process of gradually moving from all breast milk, thru
starting solids, and eventually giving up the breast.
I think Truby King said ' wean at 9 months', meaning to start solids. In some
case this has been interpreted as meaning *stop breastfeeding at 9 months*.

So 'weaning' could start in a moment, and take a while to finish !

If the person who sent the letter thought the mum was exclusively breastfeeding,
then it begins to make some *sense* ? Not trying to justify professionals being
harsh. It would have been better to check a few things first.
BTW, my night-nursed children have lovely teeth ! No fillings etc. And they
nursed After cleaning their teeth for bed !
Helena Boutal