This is somewhat restated and overlaps the other postings. Here are my thoughts on this:
The ditching speed is to provide a safe approach speed. Depending upon the seas, you may not have the ability to judge your altitude, and this avoids stall/spin issues when ditching. The reality is that this type of complication to an unfortunate situation happens frequently. There are Youtube videos of people stall/spinning in as they are doing a ditching.
Frequently over smooth water, and even rough water, the height above the water is difficult to judge. Even if you don't have a seaplane rating, find an instructor to give you some simulated glassy water landing practice. A good time to do it is when you have night ILS approaches. You can even do it under the hood, and simulate a 0/0 approach.
- Many ditchings are done with loss of power. If you are faced with performing one, try to have some fuel left, because your A/C is more controllable with a little power. From those who have experienced it, I have heard that they see the gear hit the water out of the corner of their eye (C182) or they feel the prop picking up spray (Arrow). Back elevator is a real good thing, as it may avoid flipping over, which can hurt you and be very disorienting. Also, I wouldn't compromise your ability to fly, but you might hold the yoke/stick differently, as the force of hitting the water has broken a few hands/wrists or caused dislocations. That only hampers your ability to manage everything else.
Also for preparedness, consider the FAA underwater egress course. After you've been dunked in a high school swimming pool a couple of times, it is easier to keep your wits about you when you plunk into a great lake with a 42F offshore water temperature mid-summer. Someone who has been there swears by the underwater egress course. (not me)
Also read up on what you can about ditching orientation. Like where the swells are and how you are oriented to them. It softens the bang.
A few other things: for great lakes crossings, the preflight briefing includes having passengers identify what bags, sleeping bags, or whatever that they are going to put in front of them if there is a ditching. It includes what to do if the plane gets inverted. Most GA aircraft do not have 5 point, or shoulder harnesses in all seat positions, so protecting faces is important. Also when doing a lake crossing I recommend that everyone have their life preserver on before feet wet. Because SAR at night on the water is problematic, I normally do not fly across large bodies at water at night in SE piston aircraft. Just too many factors multiplying and stacking against me. Flashlights and strobes are nice, but having looked for people with strobes over open water at night, while raining, I can say that they were very very difficult to spot under only mildly adverse conditions.
Finally, let me address then shedding of 13k airspeed. At 52k Vso, the v**2 component is 2704, and at 65k it is 4225, so you are right, in that you can reduce substantially your kinetic energy of impact. But given the likely lack of horizon, the difficulty and inexperience you are likely to have ditching, the handling characteristics of the aircraft at Vso, the downside of a stall/spin, and the possibly increased kinetic energy, the impact disorientation, etc. it is easy to see why the higher speed and better controlability of a more "normal" approach speed is beneficial.