I've not heard of this before, I am wondering if there may be the opposite going on i.e. symphysis pubis separation. This woman can only walk small distances and is in pain. Kerrianne Waterbirth is supposed to be hands off birth. A woman in the bath at home can be accomodated by kneeling by the side of the bath with a cushion for your knees when listening for the fetal heart intermittently. Tthe rest of the time, the midwife could sit on a stool or a chair.
Most domestic baths are probably easier to get out of than purpose-built pools.
Most delivery suites do not have equipment to help lift women anyway. There is no evidence to back up their fears. I agree that you should be there to meet the woman's wishes. Hope everything goes to plan. I don't find the floor comfy, getting too immobile.