Excellent deduction (and spot on).

Fair enough, it only takes a few genes to have childhood leukemia or sickle cell anemia but even with genetically identical individuals (twins for example) there are also significant examples of behavioral differences (suicidal bomber, pedophiles, etc) between them.

So it is hard to find a good number that wasn’t just a feels good number and so my entirely rough guess was based on how clonal humans are (genetically speaking).