Look non of us know the facts. That confession under torture should be inadmisable we both agree. That an admission extracted through torture can be false we both agree. If the interrogator's purpose is to extract confession no matter the truth they will get it. However torture can also be used to extract true information.
I see here the following possibilities:
1. The investigators chose scapegoats and extracted confession out of them. The interrogators have no interest in getting the truth but only to lay the blame on the Tag Mechir group.
my opinion about option 1: not likely.
2. The investigators have some evidence or information against the suspects. Maybe they don't want to reveal their informants, as Moshe Yaalon has indicated. They pursued to interrogate the suspects using 'legal toruture method'. In my opinion, this is the likely scenario. Now what follows this:
2.A The suspects are innocent. The informants gave false information. But the investigators are convinced otherwise, and they are so eager to prove themselves correct that they extract false confessions. If that is true the investigators only got admission as well the scenario with they forced the suspect to admit to. It includes only information known to the investigators as well as made up information they forced the suspect to admit to.
2.B The investigators broke the suspects through torture. They were able to extract from them not only admission but further incriminating evidence such as details that only the purpetrators could know, leftovers from their preparation of the molotov cocktail etc.
This is insane. The torture lasted for weeks including kids not even connected to the event because they had alibi. It is scientifically proven that torture produces false confessions. Accept scientific fact!
Admissible or inadmissible is a sideshow, and even the falsely produced confessions are inconsistent which only points to their being false.