That paper has nothing to do with the incident in question. You're referencing a BBC article that references a paper stating that Clear Air Turbulence is getting worse [1]
> Turbulence is unpleasant to fly through in an aircraft. Strong turbulence can even injure air passengers and flight attendants. An invisible form called clear-air turbulence
But in the incident in question, the plane flew directly through a convective storm.
> Climate models consistently project environmental changes that would support an increase in the frequency and intensity of severe thunderstorms that combine tornadoes, hail, and winds (high confidence), but there is low confidence in the details of the projected increase.
The models project it, but there is currently low confidence in the increase.
> Turbulence is unpleasant to fly through in an aircraft. Strong turbulence can even injure air passengers and flight attendants. An invisible form called clear-air turbulence
But in the incident in question, the plane flew directly through a convective storm.
[1] https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL10...