Incomplete coverage is exactly what blows the entire safety argument out of the water, not only does it not prevent someone from drinking, or going without sleep for 48 hours, it also doesn't catch drugs like LSD where the concentration required to affect the user is orders of magnitude smaller than any feasible test can measure.
If a company was serious about safety and not just giving lip-service, they would use regular impairment testing -- tests that measure your ability to do certain short but complex tasks - the good ones will catch any sort of impairment -- pharmacological or otherwise.