Colour Double Exposure

[Espermaschine]

I had another look at this effect, and dug out this YT tutorial that i had found earlier.
https://www.youtube.com/watch?v=x3xFAbX5R84

Its not very well made...so the steps are:

• copy layer
  
• paste layer (floating layer appears)
  
• deselect a channel (so in case of the red chnnel: three channels are highlighted blue, the red channel is not)
  
• offset floating layer with the Move Tool -> anaglyphic effect appears
  
• anchor floating layer
  

Now here is my question: why does this work the way it does ?

For example, if i convert the floating layer into a normal layer, the effect is gone.
Why ?