Among admits, there are small differences in actual test scores especially among whites and Asians.[1] Also, there are racial gaps among actually using SAT prep.[2] Whites may actually be the least likely to use test prep courses depending on which source you look at.[3] I guess if you are applying to Harvard, test prep could actually be pretty significant.
When Harvard makes it decisions, test prep could actually be a major factor in admission there since scores are so close(assuming the numbers you gave). Especially since they try to reach out to people in different regions of the US.