They may be trying to differentiate between high temperature as "fast", like in this case, and high pressure as "hard". Though both can lead to a particle kinet

They may be trying to differentiate between high temperature as "fast", like in this case, and high pressure as "hard". Though both can lead to a particle kinetic energy above the Coloumb barrier, in the former case the time between collisions will be lower (AFAICT), which may be important. I'm not a plasma guy though.