I think that LE's conditions around allowing Tammy's kids to view the autopsy report might indicate that they (LE) do not trust them (Daybells) to keep the information confidential, either from CD or possibly, from the press/social media. Think about it: if there are results indicating her death was not by natural means, and if any of them are still sympathetic to their dad, could they know that information without sharing with him or his lawyer? Prior is now implicated in the ownership of their family home, it would not be hard at all for them to converse with him, either.
(I see that squareandrabbet has posted nearly the same thing while I've been typing this up, but I'll continue anyway...)
In other words, I think that LE is telling the world that they do not quite believe that the Daybell kids are fully on the side of justice for Tammy at all cost, and they want to be very cautious about how, and to whom, the autopsy results are released. All MOO.