If you look at the team since we got our full unit back starting in game 13 (Crowder and Horford playing with IT), and you discard the 4 games IT has sat since then, this is what we've done:
Record: 24-9, 0.727 win%
Losses: 6 to above-.500 teams (SAS, OKC, HOU, CLE, TOR, WAS), 3 to below-.500 teams (DET, NYK, POR).
And during that stretch IT is averaging 31ppg and 6.4apg, on 53% from 2pt, 40% from 3pt, and 93% from FT.
He's the best player on a team with one of the best records in the league during that time span. (Does anyone know how to find the exact numbers on that?)
If you carve up his numbers different ways into smaller samples, there will be times when he looks better on a given dimension, and times when he looks worse. But that's the overall picture.
And, one final quibble: this is based on minutes he's on-court vs. off-court in 4th quarters. Aren't the games when he's off-court likely to be Celtics blowouts? So wouldn't it be completely expected that the team would be blowing out its opponents when he's off the court? He almost surely spends more 4th quarter time on the court against better opponents. Just my guess.