Isn't the impact of the API academics on NSS fairly minimal, relative to performance in Primary at least?
Correct. API is essentially another screening process. You pass all the courses, you are good to go. No one in Primary is going to care very much about how well you did on Aero II. Also, if you obtained a pink sheet during API, numerous sources have stated it shall evaporate into the ether.
That being said, I looked at my ATJ the other day and thought whoa there is actually a section that lists my NSS coming out of API. However, that NSS is practically equivalent to half an event or less in Primary.