The score says how it ended. xG says how it should have ended: it is the sum of the chances each shot was worth, not an opinion about the game.
Juventus created more (1.18 xG against 0.96) and left with nothing.
Sassuolo: −0.6 for the season (10 in the table). Juventus: −2.1 (7). The gap between points and xPTS is built from matches like this one.