Optional Recommendation

I’m considering applying for Stanford and am considering submitting an optional recommendation from a coach who’s worked with me for about 4 years. I’m wondering if anyone knows whether Stanford looks kindly on supplemental recs - I hear that colleges such as Harvard generally like more information about you, whereas some other competitive colleges explicitly discourage additional recs unless they add significantly to your application. I don’t know much about Stanford and the official website seems a bit ambivalent about optional recs. Does anyone know whether they may look kindly on an additional letter of rec?

An additional recommendation is generally useful only if it adds something new about an applicant or gives an added perspective that helps the admissions committee evaluate the applicant more accurately.