Because simple hot air balloons (without gas buoyancy) would not be very effective at this sort of problem. It makes much more sense to use He lift weather ball

Because simple hot air balloons (without gas buoyancy) would not be very effective at this sort of problem. It makes much more sense to use He lift weather balloons (even if they use temperature controlled solar power to maintain proper buoyancy). I'm just looking at the pictures, but they don't look/lift like simple hot air balloons to me. I'd lean toward the science writer simplifying the language.