they reported to my boss that the urine test was abnormal and would require further testing which could take up to 72hrs… it sounds like a prelim positive that is going for gc/ms confirmation.
Sounds like what youve heard is a BS story. If a urine sample tested positive on the initial assay screen, it would subsequently get sent to the confirmation GC/MS without the MRO notifying the employer that the "sample requires further testing".

Have you found that the home tests are not as sensitive as Labcorp?
The lab assays used for the initial screening function on the same principle as the home assays. Therefore neither are more accurate than the other.