Why does my doc pee test me for methadone, but the test only tests for opiates so methadone wont show cause it needs a specific test right?

Yes, it will. Urine drug screen tests for opiates, thc, Methadone benzodiazepines, methamphetamines. Other test done are hair tests.
Urine analysis. Urine tests are administered routinely to patients undergoing any detoxification treatment on an outpatient basis. This is to make sure you are not using other opioid medication which while on Methadone could be counterproductive and dangerous.