Exactly as it would "just" solve the use case without getting into the castes system specific worry. E.g: Candidate selection should be based on the skillset and fitness of individuals for the scope of work/description, without discrimination attriuted to personal affiliation, ethnicity, religion, gender or sexual orientation, difference, + "group identity", . The employer would thus commit infringement if when faced with two somewhat equals in fitness candidates he folds some individual based on gender or whatever else that falls into personal, group identity factor or affiliation to a certain group. I think it covers the caste system issue we see at the workplace without having to talk about castes in the legislation, and the benefit is that it allows the text to cover other group identifications.

Btw we have other avenues, anti discrimination is one that covers shutting down labelled candidates. Nepotism is described as favoring relatives or friends, just add "or group identified with" to it and boom that covers the caste system issue (and beyond). I'm no legalist so of course I'm not drafting a clear definition of group identity but you get the idea, i hope. I suspect we are stuck on this because on some side we have identity politics and quotas advocates wanting the legislation to accommodate their wishes, hence forbidding group identified favoritism in the law. This avenue is being at best ignored as a potential simple solution, at worst battled against with teeth and nails for other unrelated motives.