How do wedge brakes differ from S-cam brakes in how they apply the brake shoes?

AAMVA CDL Manual, Section 5.1.8 (Foundation Brakes - Wedge Brakes), p. 5-2; 49 CFR 383.111(b)(1)

Drivers who move between vehicles with different foundation brake types should recognize that wedge and S-cam brakes apply force differently, which affects adjustment procedures and what a pre-trip inspector looks for at each wheel.