During a quiz attempt, users interact with three pages: mod/quiz/attempt.php, summary.php and review.php.

attempt.php and review.php are always displayed with at least one block region, because the question navigation gets added as a fake block.

Therefore, in some themes, there is a big visual jar when you go to and from the summary page. I think that is bad, but the only way round it I can think of is to add an invisible fake block to the summary page (and then display: none it).