Sending only one SAT subject test score

My child was scheduled to take the subject test in October, but it was delayed due to weather and he could not attend the makeup date. He took them in November, but was sick on the test day. He intended to take 3 tests, but left after the second one due to his illness. He got a 770 on Math II but only a 690 on Bio (the second test he took. BTW AP Bio score of 4 even though he took college bio, not AP).

He has great stats, 2250 SAT, #1 in class, great AP scores, great EC’s, and is a competitive applicant who intends to study engineering. We know that Stanford say the tests are not required, but that seems to apply to applicants who cannot afford the additional testing.

How would sending just the 770 Math II look to Stanford? It is likely they would assume he was hiding his other score, but he does not want to harm his chances by sending the 690. Is it better to send nothing than to send one score? TIA!

Some people only take one test. The subject tests are completely optional and admissions has said in the past that even submitting low scores would not harm the application. I know at least two people that have gone to Stanford without taking any subject tests.