Why? You think if he was such an all powerful being, he could make DNA that didn't have sibling problems. You make him sound like a hacker banging out a quick and dirty work around to a bad initial design.
Why would the capacity for genetic diversity be an indicator of bad initial design?
I didn't make God sound like anything. I was throwing out ideas. You're the one making inferences.
A perfect creation, I would imagine, had one one set of traits per gene, all dominant. However, because the affects of time, the enviroment, and sin in the world after the fall of man, mutations, in an otherwise perfect creation, manfested themselves as recessive traits, and sometimes as dominant traits.