Extracurriculars are another dog-whistle for that sort of thing. A heuristic like "Deduct 150 SAT points for violin or piano" would be pretty predictive.

While this is true, I don't see why this can used as justification to keep name and ethnicity showing. There will always be ways to guess an applicant's ethnicity but since it (supposedly) has no bearing on admissions, why keep it in the application?

Not once it becomes known - I imagine Amy Chua types would stop forcing their kids to learn it, and applicants would stop mentioning it on applications (unless they are applying to Juilliard).