Can I JUST send my SATII and ACT?

I’m applying to Northwestern, who has a score choice policy, and I took the SAT twice but still did far better on the ACT. I want to send my SATII scores because I did very well on the Math 2 subject test, which could make up for my lower math ACT score.
However when I go to send them on the SAT website and try to uncheck my SAT scores, it gives me a warning that “I’ve chosen not to send a test score that the SAT score-use practice requires.”
However it seems like Northwestern requests SATII scores even from ACT senders, so I don’t see why they wouldn’t allow you to not send your SAT scores.
Any help is appreciated!