If they have any time left over at the very end, can they go back to questions in earlier sections that they guessed?
Why is it done like this for just NVR - it sounds a weird way of running an exam? I would have disliked the interruptions.
Maybe one reason for having the split sections is that the answer sheet doesn't have any answers as such, just a,b,c,d,e. It is possible, as proved by my daughter in her practice paper, that you can answer the questions out of sequence without realising it. If you had no split in the whole paper you could get to the end with all the answers out by one. At least this way you can notice an error at the end of the sections!