I may not be right, but I try to argue soundly. The thing with the demo version I advised for, was because of observation. I noticed games with paid only content having less ratings and followers and comments than pay what you want games. This still might be a fluke, because of what games I did browse. Maybe there are paid only games that fare better, because they are paid.
Having success as an indie game developer is a bit like having success as an indie musician/singer. There are just so many people trying it. It is hard. Even if you do everything "correct", you might still not have success and frustratingly see projects that did many things wrong yet still are more successful.
Oh, and you observed first hand what a demo version could have as an effect. People posted videos on youtube while playing your demo version. Maybe you got some followers due to that.