@yonceonhismouth the following link http://admission.stanford.edu/application/freshman/testing.html states
SAT Subject Tests
SAT Subject Tests are optional. Because SAT Subject Test scores can highlight your areas of strength, we welcome the self-reporting of these results in your application.
I know instructions can differ on different parts of applications/websites and what you are saying is what my notes for Stanford say so can you tell me where you are getting your information from?