Is the way we’re handling promotions discriminatory?

Q: “For nearly every job family at my company, staff promotions are handled in a calibration meeting with senior management who discuss promotions and raises. Promotion requests are defended (if necessary) with examples of sustained high-level performance. The only job family held to a different standard of scrutiny/justification are our administrative assistants. In the case of their promotion from one level to the next, a special committee has been formed and managers come before that committee to plead their case for promoting their admin. A substantial number of requests are denied, usually with ‘she doesn't support a senior manager’ silliness. I've cautioned my managers that creating this extra hurdle for promotions for a single job family is inequitable and discriminatory. Am I wrong?” – Anonymous, Washington