Well, the author was talking about organs, not genes. Generally speaking the organ arrangement described in the article (external testes, internal ovaries) is pretty well conserved among placental land mammals even if genes related to other aspects of reproduction are not.
The author is wrong in saying that the testes are not protected, though. They're quite well-protected, with a leg on each side. Simple proof of this is that it's clear when these are damaged due to the pain, but most men will only experience this pain a couple of times in their life.
The testes are even more protected in quadrupeds, far away from any frontal fighting or sparring. And if you're a quadruped that is being chased by something that can damage your testes from behind, you have far bigger problems than damage to your testes.
