I'm pretty sure that since it is a "History and Physical" Exam, you only have to diagnose. Therefore, the simulated patient may present with some musculoskeletal problems that would require OMT, but you would only have to diagnose and document the lesion. It would be totally voluntary if you wanted to actually "treat" the lesion. This is how it was explained to me by an NBOME official.
Also, only 25% of the 12 patients (3) will have an OMT-related problem.
However, I wouldn't trust this 100%.