You are correct. If they hit the ceiling it is on them. When I travel when the seat belt sign goes off I will loosen my seat belt a few inches for comfort but never take it off except for going to the bathroom. The air hostess will walk about during the late stage of climb to crusie altitude as they prepare for drink and meal services.
Forgot to add this. The SW flight was definitely under positive control by ATC. If that Hawker Hunter jet was on a trip to ELP it would be climbing to cruise altitude of about 30k and under positive control by ATC.
Unless the Hawker was violating normal IFR flight rules, this is on ATC.
I well remember ATC giving me vectors into a Thunder Storm many years ago. I was given a vector and then saw and heard a lighting bolt just a few hundred yards away, I was IFR. I politely said, N65—D declines the vector and please get me out of this storm. When I got on the ILS I could not hold proper altitude withing 100 feet due to extreme turbulence. At 1000 feet I broke out into perfectly smooth air and great visibility. South Louisiana Thunderstorms can be fierce in August.