So you are saying you didn't read the paper or abstract. They sort of covered that entire topic. This is about strength not "health", they took that into account in the study.
By taking it into account, they probably excluded people with medical issues that would skew the results. The study isn't perfect, so this guy has a point: People with genes that make them naturally strong may have related genes that contribute to their overall health. And the converse may be true for weak people.
There is no such thing as naturally strong... there might be some genetics in how quickly you can gain muscle strength but no one is born strong. To think of it conversely, if a limb becomes paralyzed, that limb will undergo extreme muscle atrophy no matter who it is. Also, they listed as a mean 83kg for bench press for the "upper third". This is not a very large amount of weight and is easily within the genetic limits of the grand majority of men.
You can't be serious. Took it into account? Before accusing people of not reading, consider they read it more closely than you. A study isn't "covering [an] entire topic" by just mentioning the word "confounding" and throwing a few possibilities of easily measurable factors around. This study is downright pathetic.