This happened to me, 11 years old at Scout camp. No injuries but some serious ribbing for months.
Yes, if you are not used to bunk beds upper, you could roll out during the night....................
Attended a men’s retreat some years ago at what was a Young Life camp near Asheville, NC. The cabins had three-level bunks and one of the attendees (was in his 60s) fell from the very top bunk, sustained massive head injuries and ultimately died as a result. Was a very tragic accident at what otherwise was a great retreat.