"while peristalsis will have shut down, enema will/can promote full evacuation of bowel?
Not only in early days of fast, but, say, 3 or 4 weeks in, as waste accumulates due to fat being consumed??
If you take a water enema the first 3 days (you can take it even 2 times per day, if it feels good, it may help with food cravings and with hunger) it will help eliminate most of the food you have eaten before you started fasting.
If you take a water enema, lets say on the day 10, or 14 or 21, it can help eliminate accumulated bile, dead cells from intestinal lining, mucus secreted by intestines, etc .... in other words, if your bowl is lazy, it may accumulate a lot of things during the water fast.
Some people estimated that several kg of dead cells may be accumulated inside bowel during a long water fast, not to mention several liters of bile and other digestive juices.
There are even people who take a water enema every 2-3 days of their water fast, and swear of the benefits in terms of energy, healing, and wellbeing.
Many people experience serious unpleasant symptoms during a long water fast, and at least some of those symptoms could be prevented and/or cured by keeping the bowel as clean as possible.
It could be good to use water free from chlorine, so boiling the tap water before taking a water enema could be smart, if you have no some better source of water.