Virtually all refused refugees do ask for the pre-removal risk assessment. I would think it's in the high 90%. Although perhaps some feel it is safe to return to their country, for the most part, if people are asking for refugee status, it's because they believe it's unsafe.
But if they don't apply for the pre-removal risk assessment, if they say they're not interested in it, then the removal officer books a flight for them and they leave in the next few weeks.