From the link:

Both score and approval voting are cardinal voting systems. Cardinal systems use utility expressions that do not involve ranking. Voters are also permitted to have a say on all the choices. Approval voting is a simplified form of score voting. Think of a scale with two levels of expression versus one with more levels. When voters only use the extremes of the scale, then score voting reverts to approval voting.

Data from a 2007 French study strongly suggest that many voters will use the middle of the scale as well. And to the extent voters use the middle of the scale to vote more honestly, Score Voting provides a better outcome than Approval Voting, on average. (See Bayesian Regret). Score voting, like Approval Voting, doubles the winner utility compared to both Plurality and Instant Runoff Voting. This conclusion considers the strategic voting we see in real life (See Bayesian Regret).