This shocked William for many reasons. First, he crossed lots of distance until arriving here. Then it was the time issue.
He didn't know what date today was, what month or year. But from the words of these masters, he knew they spent more than what they felt.
They spoke as if the Hot Snow area lasted for days here. And that meant it moved from the place they entered from to here, taking days, even weeks in doing so.
He knew the reason behind its sudden disappearance was for him to pass through the exit. However, the process that seemed to take a few minutes took long hours in the real world.
William knew they noticed the shock on his face, and he explained this by saying he was scared to end up in that terrifying place. They bought his words, especially with his younger appearance and look.