It may not be wrong.
230.90 Exception 3 allows the total rating of the overcurrent protection to exceed the conductor rating. However the calculated load must be less than the conductor rating.
You did not say the size of the service conductors but you did say 100 amp so a 6 AWG GEC may be the right size. GEC size is based on service conductor size not the service overcurrent protection.
I do not think I would rip this out unless the customer wants to exceed the code minimums.
Bob
