Starting them is one thing but it comes down to starting and switching, for example I start everything on mice for 1 simple reasons, I get a higher success rate on getting started animals early if the first 2 to 3 meals are mice compare to rats, however snakes that I sell are all switched to rats (I switch them usually within 3 to 5 meals)
Does it make a difference? Not sure if my buyers care or not but the sooner you switch an animal the easier it is, and some people might not know how to do that efficiently or not wanting to bother with switching which can take time, and ultimately feeding rats is what people do because one prey is just more convenient.
Personally do I care nope I actually never even ask what prey type the animal I am buying is eating, because I know that if it's a young animal I will have him switch in 5 to 10 meals.
Ball pythons do not generally imprint on ASF like they do mice or rats making it easy to switch them to either, but you need to be upfront with the buyers and let them decide if they want to take a chance.