I'm going to disagree with that. I just think that if there was a plan or prior knowledge on Smich's part, the texts between him and Millard simply don't make sense. First, DM texts Smich to be out of sight when he gets home. You can interpret that in several different ways. Not long after, Smich is texting Millard for food money. To me that doesn't make sense at all. If he indeed knew what was happening upstairs, why would he send that text? There is no contact between their phones for the next few hours when the crown alleges the crime was being committed. Might make sense but Smich then texts Millard just after midnight as when Smich texts Millard asking if he's around. Doesn't make sense if they were working together. On the 4th Millard is gone before 9:00AM without Smich. Smich sleeps till about 3:00PM. Again, it doesn't make sense if they were acting together.
Yes, Smich knew about the incinerator and its purpose, but I think that he may have been under the impression that it was for future missions (TB). I think he became aware of LBs murder at some point that night. I think he was all in on disposing of the body. But I think this was all Millard's plan.