Not that unusual. Just a month earlier, 25 passengers were injured on a flight coming into Hawaii from Phoenix, 6 of them severely enough to require hospitalization. [0]
"Between 2009 and 2021, at least 146 people, including passengers and crew members, were seriously injured by turbulence ..."
It’s precisely because we’ve treated these “rounding errors” seriously that aviation is so incredibly safe. It didn’t used to be, it got that way because the engineers treated even a single injury as an unacceptable failure.