When I first saw position sul, I thought that was the dumbest thing I had ever seen.
This doesn't happen very often, but I was wrong.
I've since tried it, and it gets me on target- accurately- much more quickly than a low ready. And if you do it correctly, it's almost impossible to point the gun at your feet, as I had originally thought.
As for reholstering without looking- I've seen people get cover garments, or just their regular garments tucked into a holster by accident, just during range conditions, not under stress. Without looking, you risk that something might catch the trigger and fire it in your holster. This might be a cover garment, a damaged holster, or some other foreign object.
With looking, you risk that another attack is going to happen in the second or two you look down to ensure your holster is clear. This is after you've already determined the situation is safe.
Either way, your gun is now holstered. If another threat appears after that point, your reaction time is going to be about two seconds anyway. So, really the two seconds you're looking at your holster doesn't hurt your reaction time any worse than having the gun holstered. IMO, if you're secure enough to holster, you're secure enough to look to ensure your holster is clear.
In either case- snagging a trigger vs. an attack while holstering- the risk is so minimal, you could go either way with it. I think the bigger risk is that the situation is not safe after you determined it was. If you really want to do something to enhance your safety in the aftermath of a gunfight, the bigger is learning to check your surroundings or getting to a safe place after a shooting.
(Bear in mind, the safe place doesn't have to be 4 counties away, like that guy in Jacksonville last week.)