I have to agree with you to a certain extent. Often the manner of death is with-held in MANY cases, and for good reason, such as it is specific information that the knowledge of may indicate direct involvement. The with-holding of that information can be detrimental to a case, and I agree, pointless to provide to the public.
I have no idea why a toxicology report would be with-held, especially if it is not related to his death as was stated. That is unusual, and I can only surmise that with-holding it means something as much as releasing it would, to be honest in my opinion. Toxicology tests aren't even mentioned in some homicide cases in the first place. For some reason, in this case, the fact that it was being investigated was very well known, only to then be with-held, and eventually reported as not significant. That is odd, in my opinion.
What I find completely ridiculous is how we keep hearing about this shoe and cell phone. IF this whole case's chance of resolution lies in the balance due to the lack of these items, that is a bleak picture. I'd be shocked, by the way, if they actually surface ever, especially after all the publicity about HOW important they are to find.
I think you answered your own question when it comes to the toxicology report. If they don't think it had anything to do with his death there is no reason to release it. I mean, if a man is killed by a co-worker over a dispute at work and the police find out through the course of their investigation that he was cheating on his wife there is no reason for them to release that info if it didn't have anything to do with his murder. It just isn't necessary. The only reason to release it would be to satisfy those who are curious, but it doesn't help the investigation at all.
With the shoe and the cell phone I think the important part is WHERE they are. Their location tells police one of two things -- either that he was killed there, or those items were dropped there after he was dead which would give the police another data point as to where the perps have been since the murder. The physical items don't provide much value, but their location does.