I just don't think they wouldn't have informed the family immediately or at least within a day or so (this was 3 days after finding the RAV4 and we know they went into the vehicle the next day). At the time this article was written, MH still sounded hopeful, it's odd IMO, considering that not only was there blood in the front of the RAV4 (and they wouldn't have known who's it was at the time, would they?), and there was also blood in the back and spatter on the rear cargo door. Although it wasn't conclusive evidence... it was a huge clue. Not to mention that Brutus hit on the RAV4 too.
As for the search warrants... I think Kratz was blowing smoke. Here is the search warrant file, you can see a list in the first few pages (remember the article was written on the 8th).... the only one I see that is not connected to the Avery's is for Cingular, and it wasn't even served (and it was many days later, on the 17th). Unless he meant the the warrants for DNA, which is technically not property LOL I'm not sure, but I would have thought it would be part of the file though. In all the documents I have read so far, they didn't even get a warrant for Zipperer's, although, the Zipperer's eventually, somewhat, kinda sorta, reluctantly talked to the officers.... after knocking for 15 minutes and talking to JZ through a window.
http://www.stevenaverycase.org/wp-content/uploads/2016/02/Search-Warrant-File.pdf
ETA: I guess I shouldn't say it was odd that he was hopeful (I think a family member should always be hopeful until they have concrete proof)... I find it more odd that he said there was no sign of harmful acts, when clearly the blood in the RAV4 said otherwise, especially the spatter and blood in the rear. IMO