Given that Harvard recently made SAT Subject Tests optional for students who cannot afford to take the tests – or for students who want to have their applications considered without them – your SAT-ACT test scores would have to be soooooooooooooooooooooooooooooooooooooooooo exceptional (read 2400 or 36) that it wouldn’t matter any way whatsoever if you submitted SAT Subject test scores or not.
Bottom line: Unless your have a perfect test record and cannot financially afford to submit SAT Subject test scores, your application is at a disadvantage if you don’t submit an SAT Subject test record. (FWIW: Even though Harvard looks at your application without regard to whether you can afford to attend the college (need-blind admissions), Admissions can still see if you have applied for a fee-waiver. Those students applying for a fee waiver are generally given “a pass” when it comes to SAT Subject tests. Those who do not apply for a fee waiver are at the mercy of the Admissions gods.