Adam and Eve would have been created perfect which would mean no genetic mutations and it's not unreasonable to conclude that they contained all the genetic information necessary to account for the variation we see in humans. At the Fall is when corruption entered the world but it still would have taken time for mutations to occur and spread throughout the human race enough so that inbreeding would allow harmful recessive traits to show.
The laundry list of reasons why two people alone could not produce the variety we see in the human race now would only apply to imperfect humans in today's world. Perfect humans, or creatures of any kind, would have all the DNA they possess availbalbe to them for use, there'd be no *junk* DNA. So what would the potential be in a creature was able to utilize 100% of the DNA is possessed?
(it's not unreasonable to conclude that they contained all the genetic information necessary to account for the variation we see in humans.)
How is that not unreasonable? It is totally against all we know scientifically. There is no way two people can carry all of that genetic information! Define "created perfect"? Did they have more chromosomes than usual? Were they even human at all?
Based on what we know about genetics and DNA, the Adam and Eve story is scientifically impossible. This is one reason why many people discount Christianity whole cloth. You are asking me to make huge leaps in logic to believe stories like Adam and Eve, Samson and Noah's Ark.