That's not what happened at all. The college board admitted their fault and are letting students take the test again. Even without that, they mentioned in their FAQ that JPEGs and PNGs are the only file types acceptable and even sent out a tweet (which should have been an email) a week before especially for iPhone users to let them know how to take pictures as JPEGs.
I agree with the people blaming the board for not having a standard image input field that lets the OS know when to convert images to JPEG but that is their only fault and I wouldn't have thought of that as a bug deal if not for this issue. While I'm all for open source media formats replacing what we have, HEIC certainly isn't big enough to be considered as among standard input options. Also, isn't Apple themselves infamous for not supporting certain formats throughout their devices?