However I do have a problem with the first piano clipping segment. He was able to lower the volume with no clipping because the initial recording did not clip. If the piano was recorded with clipping no matter how loud or soft you make it it will still have clipping.
Yes, this technique in Reaper assumes that the original signal is without clipping.
What I find pretty clever is that if all individual tracks are recorded without clipping, and even if clipping is present on the track due to poor volume settings, this can all be fixed in the final output very easily with the JS smoother plugin. Moreover, when the plugin is placed in the correct position in the chain, it can enhance the use of subsequent plugins in the same chain. I was never aware of any that before. Thinking about it, though, it makes sense (I'm just slow).