It is an alternative eroticism which as she says is denied and we have lost sight of, these days only understanding erotic to mean sexual, as reflected in the reactions to the comment
Possibly because that is what "erotic" has always meant? If she meant some sort of alternative physicality "erotic" is a terrible choice of words.
Psychoanalysis and a lot of the history of psychology did in fact use “erotic” more widely than just genital sexuality. Literary critics and philosophers too in the 70s-90s - eg in the “erotics of the text” meaning a kind of tactile joy in reading which is erotic though not strictly sexual.
One of not just Freud’s but the whole history of twentieth century psychoanalysis and psychology’s insights was to view the development of the human psyche as intertwined with a latent erotics that manifests itself in all sorts of physical and material relationships that humans have with each other - not just the narrow idea of “genital sexuality”. The mother-baby dyad is thought of as one of - perhaps the most important - of these, making possible the baby’s future healthy relationships with others. It’s tactile, loving, mutual and physical. The baby’s later psychosexual development builds from a healthy relationship with the mother and their physical enjoyment in and with each other. The mother is the baby’s primary love object and all later relationships are psychologically formed as developments of that model. That’s what Greer is referring to.
It used to be a well understood idea based on a complex and rich history of developmental psychology; and to misunderstand it in a kind of “ew, that sounds wrong!” kind of way is evidence of how fast we’ve retreated into a kind of mechanistic, moral simplification about the human self, both in gender ideology and ideas about sex, but also right across the human sciences, psychology and medicine.
It’s eye popping to think that people today will think all sorts of “kink” is perfectly normal, that would have been considered well outside the normal and acceptable range of human sexuality forty years ago - and yet are disgusted by the idea that the mother-baby relationship might have an intrinsic erotic tactility about it?