Some women, after one or more childbirth, sometimes, have the interface between the rear wall of the vagina and colon a little relaxed and and to defecate they are forced to push more. So, they adopt for themselves this position, easier specially in their case. This position prevents constipation, haemorrhoids and all diseases related to the long retention of toxic matters in the colon, may be cancer.
Women never mention this.
The ideal : behind the olivers, or the baobabs as you have !