In the playoffs?I'm not going after your larger point.
I'm just saying you've been drawing the wrong lessons from the stats. Smart comes out well. If you remove the small-minute players (which I think you should, because the sample size is too small to be trustworthy), he's almost always among the top five of the Celtics, sometimes in the top three, despite being on very good teams with other high net-rating players (Horford, Irving, Brown, Tatum, Hayward, for example).