I dug into the line ups a little. Tatum played 13.2 minutes on the court with Horford, Pritchard, Hauser (3 bench guys), and 0.5 min with two of the 3. Brown played 0.5 min with 3 bench guys, and 6.3 with 2 bench guys. This continues a pattern from the regular season where it is Tatum that is generally anchoring the bench unit over Brown. Brown was more the bench anchor last regular season.
I wonder if this is the best thing if one of the goals is to have Tatum at his best at the end of the game. I would think that when he is on the court with 3 bench guys vs the starters, that he expends more energy. If you expend more energy through the course of the game, you are going to have a little less at the end, especially if you are playing more overall minutes in the playoffs.
Another thing with this is when it was Tatum but not Brown, BOS was +3, Brown but not Tatum, +17. You could look at that and say Brown was better than Tatum, but most of that time without Tatum was when Brown was on the court with all starters except Horford in for Tatum. In the time it was Tatum without Brown, most of it was 3 bench guys and either White or Holiday.