Yes, Yale is flexible but they want scores from 11th grade or external exams with results before application date (so, a November test date for IB would work for someone applying RD). Unless they changed it recently, predicted results didn’t work.
I may be mistaken wrt Harvard because as of now I haven’t got an applicant in the pipeline so I’m just memorizing the different changes but didn’t look it up. 
US colleges would have to modify the UK version, but something could be done with this system for students in the AP system.