If the product is described as having and adjustable current limit, then it probably has extra circuitry to control the current, as opposed to just relying on an over current limit that might be in the PWM controller.
The biggest market for controlled current buck converters is for battery charging. When the battery is discharged, it's terminal voltage is low, and a low impedance constant voltage supply will often shutdown or fail because the battery will take as much current as it can if the supply voltage is higher than the state-of-charge battery voltage is. For that reason, you need a supply that has both a current limit, and a voltage limit.
For example, a 1 amp charger single LiIon cell will deliver a controlled 1 amp of current into the cell as the voltage rises from 3 volts to 4.2 Volts. At that point, the voltage will stay at 4.2 Volts as the current tapers off to near zero.