I too hate being called “mum” in medical appointments
Being called 'mum' in this way in appointments is a completely different issue to the erasure of the word 'mother', but Zoe seems to mix the two up.
The first is a lazy if no patronising way to refer to patients. Maybe not always meant to be so, but this use of 'mum' instead of the woman's name frequently belongs in the same basket as medical professionals who would use infantalised language such as 'tummy' or 'tummy-tum', or call their patients 'good girl'.
The erasure of the word mother is the erasure of biological language, very much tied to an ideology shared by a minority of people. Not the same thing at all.