I guess that is one way of attempting to rehabilitate arguments, often made here on HN, that Assange would never ever under any circumstances be extradited and had no reason to fear extradition.
Reframing that as being not merely about being extradited but being disappeared helps shift emphasis away from the other 90% of the conversation surrounding extradition fears, that proved in the end to be true.
Edit: The fears about harsh treatment were legitimate as well. Look at what happened to Chelsea Manning, charged with similar crimes. Chelsea Manning was subjected to 23 hours a day of solitary confinement, put on suicide watch, checked on every 5 minutes, forced to be "visible" at all times while sleeping, and ultimately their treatment was investigated U.N. and condemned as inhumane.
I don't understand what's so unreasonable about suspecting Assange would be subjected to harsh treatment when that's exactly what happened in the closest comparable case.