I personally am still not buying off on terrorism/criminal activity. I am in the turned back due to some sort of system failure (return to departure point and "safety" of known airport) and then after that a possible crew incapacitation maybe linked to original system failure.
Malaysias "conclusions" may be a failure to own up to error in original SAR and incident response. There is some obvious momentum to the terror angle and they are jumping on the train to deflect attention away.
My opinion