These projects attempt to simulate AM radio in most of its characteristic effects by "macro-modeling" the actual signal chain from transmitter over ionosphere to receiver and speaker, recreating the interdepency of on-channel and off-channel signals in the receiver.
This goes way beyond simple filter and distortion type of AM simulation, it recreates most of distance-related detrimental effects of AM radio like characteristic intermodulation and distortion effects created by off-channel signals, multipath propagation/selective fading and in the (cheap) receiver frontend.
Typical offchannel signals/interference are created in realtime. In addition to that special noise, you can simply add audio files on the "splatter" tracks in order to create a realistic frequency neighborhood, they will rock your virtual IF filter slopes almost like the real thing.
The bottom line is, when you need an AM sound that won't get debunked as "bandpass with distortion" [...] this is supposed to do it.
Here is my demo of his REAPER project (AM_Radio_Sim_41m) in action. The first 1:20 of the video is the original audio and the rest is the shortwave simulation. You will notice that just after I switch on REAPER I move the transmission and fading levels up and down to experiment with creating a sense of deep signal fading.
I'm sure I'll be using this trick to add long-distance romanticism to some of my home-made music mixes!
Update: below is a somewhat more realistic simulation of shortwave audio artefacts. It's a "recording" of an imaginary station that I came up with and called "The Voice of North Sudan". Here I keep moving the transmission and fading levels up and down constantly to create a more realistic audio fading pattern.