I think this way of grading is terrible. And everybody should ask to have their grades reviewed. There is no way on earth the outcome they have right now would match what they’d actually get by way of doing the actual exams.
That said, I’m not sure how they could have carried out the exams. They’d need to use large halls (which I guess they do have) and then lots of small pupil numbers over a fair few weeks to get the whole year in.
I’d have opted for that over guessing based on their work through the year. Not everybody would have put in 100% during the year, yet at the exam they’d have give it their all.