Then why do you even "make" the assumption? In any case, you apparently miss the fact that something which possesses 10% more than something else cannot be 98.5% nor even 95% identical with that other something. To talk about a subset of the comparison without describing the limits of that comparison is not very useful. I would hazard to suggest that a child's DNA is not close to 100% identical to either of the parents, unless there is some unusual genetics going on. I would also say that a child's DNA would be almost exactly 50% identical to either parent.
Before we wear ourselves out arguing about this point, what exactly does the author of the article mean when he says that the chimpanzee genome is 10% bigger than the human geonome? Number of chromosomes? Number of DNA pairs? Number of “genes” (i.e. DNA groupings which appear to effect phenotype).
And on the other hand, what exactly does a geneticist mean when he says that the genomes of two species are 50% or 95% or 99% identical? Or 50% or 5% or 1% different?
The fact which I consider more interesting is that there is much greater variation among individuals within the chimpanzee genome than there is among individuals within the human genome, not withstanding the enormously larger numbers and geographic distribution of the human population.
If variation within the genome is propotional to the age of the species, then Chimps have been around a lot longer than humans.