I contacted ANA just to be sure, posting the response here for future reference (in case anyone searches for this question and finds this thread in the future):

As the Economy N-class ticket on Singapore Airlines is not permitted for mileage
accrual, it is not eligible and the points will not count towards ANA Million Miler
program.

Quite disappointing, I guess I'll be accruing some SQ miles that I don't really need / use, and that will expire in 3 years...