While a sliced low approach is not necesarily the most desired return of serve against a strong serving Div1 opponent, it sure does beat hitting the net, hitting long, or hitting wide.
Those guys are used to serving well into the 125's and kicking head high second serves. It would be rather impossible for a 4.0 to step in and hit topspin winners off those serves.
Just getting it back to NML low is a victory in itself. After that, the point is basically nuetralized, and a former 5.5 will almost always beat a crippled 4.0.