Why does the CDL manual instruct drivers not to swing wide to the left before starting a right turn in a large vehicle?

49 CFR 383.111(a)(10); AAMVA CDL Manual (nhcdm.pdf) Section 2.7.6, p. 2-18, 'Right Turns'

Right-turn-related crashes with vehicles trying to pass on the right are a recurring real-world hazard for large trucks and buses because of their wide turning radius and off-tracking. The manual's correct technique, keeping the vehicle's rear close to the curb and turning slowly rather than swinging left first, is a specific, testable procedure that protects both the driver and nearby traffic.