We have a Haas TM1 used for a number of recurring parts one of which is the string termination part for bass electric guitars. The first program was finger CAMed at the machine and took less then 2 hours of spindle time each. The machine had a control problem and all programs were lost.
They then bought one seat of CAM for Solidworks, the first time the program ran the tool crashed right into the fixture, after this was corrected the program took nearly 4 hours to run the same part with no visible improvement in surface finish or accuracy.
It is not important to model the workholding, it is important to know where it is however.