Don’t think it’s really a mystery. ]Not sure they were able to get to close to the area where he was found and there wasn’t much left.
I think what the guy was saying is if his body was there the dogs should have found it assuming training, etc was good. It's either a criticism towards the K9 units and searching of the teams OR it's a way of explaining why his remains weren't located sooner.
As far as there wasn't much left, the partial remains is the condition of his body was at the time of when his remains were physically found. We have no idea how long he has been there, if something accelerated his decomp. No one can say that the condition his body was found in was the same condition it would have been with K9 units in the area. I don't think they've given any sort of timeframe for estimated time of death yet.
They were searching swamps and other bodies of water and wooded areas so it's not like they stayed away from harsher terrain. According to the investigation they had "air units, we have drones, we have the swamp buggies, air boats, multiple law enforcement agencies, we have ATVs, we have UTVs and we have officers on foot as well." So they didn't just rely on "on the boots" or even just strictly land. If they saw something from the air or from the boats I would assume they would look more closely into it.
Being underwater at least according to DLgal's post wouldn't hinder the K9 unit just by the nature of the water part (the particular K9 could have been impacted that's a possibility) and the handler quoted does back that up by saying "If the body had been there, when they went by with cadaver dogs, and the body had been there for more than two or three minutes, the odor would have come through the water."
While I wasn't saying it was necessarily a mystery putting it that way there's not any clear understanding of how his remains were missed during the searches which was a topic of discussion or if it wasn't a case of being missed but rather his body wasn't there when they searched over time which was also a topic of discussion.