The 3 day wait, in my experience is simply the amount of time it takes the charge (which is approved and vetted) to go from the cc company to etsy. It is a standard amount of time - sometimes it takes a little longer, sometimes a little quicker.. but three days is the time the money is in transit.
In this case, i believe (correct me if I am wrong) that when we use "direct checkout" we are basically using Etsy's portal for the money. So when a customer makes a purchase, the charge is through etsy's portal, and the money is in transit. When the money gets into etsy's account, it is available to the seller..
and then it may take a little while to transfer - although in my experience with dc money, it moves really quickly..
We are (as sellers) still liable for errors on our part (not as described, not shipping, etc..) but if there is fraud by the customer, then etsy will work that out with the cc providers..
It is no different from any other cc system. kind of cut an dried. "Risk" is maybe the wrong word here..