Except in this case the medical examiner did not come out and say there were three causes of death. A Coast Guard officer who never examined the body said one thing. A police officer reported something else and the medical examiner gave the final answer.
But in your hypothetical it's a case of the same person saying three different things. In the actual case before us it's a matter of three different persons at differing times who had differing levels of information saying different things. So you're rather disingenuously changing the facts underlying the question.
The drowning statement was done as a preliminary cause of death. Preliminary causes of death are just that -- preliminary. They are done without full information and without the clinical and forensic methods done in a full autopsy.
The other statement at issue is the Coast Guard Commander claiming the cause was internal injuries. Here a quizzical mind should be asking the question "How the hell does someone in the Coast Guard involved just in the rescue operation purport to gauge internal injuries?" Or for that matter "How the hell does a Coast Guard Commander -- who has no medical training -- purport to state this conclusion?"
The article pulls a fast one on this point: "It seems the Commander would have received this information about Fuddys injuries from someone trained to make such determinations or why would he repeat it." Well, gosh, in the absence of identifying this "other person" and verifying that person in fact had the requisite medical training, the author's assumption is one big case of JUST MAKING IT UP. Right?
So your mistake and confusion stems from your giving equal credence to these three statements. Only one (the autopsy) was a complete medical/forensic investigation that supersedes any earlier, preliminary supposition.
Ergo, no conflict.
That's what the article is pointing out.
And the author makes the blunder of giving equal dignity to the three statements without realizing the one (the autopsy) is based off superior information. You here make one