When you are using so called 48 inches (or any other length) machine, generally attachment arms are shorter than the blade length.
Therefore, the end of blade will flex upward and reduce the effective smoothing width.
With Full-Track system, the elongated attachment arm supports the full length of the blade so none of the area of the blade is flexed.
The Operator is always sure that he/she is finishing the full width or the
Full-Track of 48 inches (or any other length).