I saw that too...How can something using Electron be highly efficient? Maybe they are talking about the interface and not the system resources the app uses.
Both interface and performance actually. I have a library of about 1000+ songs and it barely takes anymore than 130 mb of RAM for me. This is actually better than some native c# music players that I used before I made this. And CPU usage is very light.
Clementine doesn't use Electron and consumes more of my memory and UI is ugly. Before we start talking about resources maybe we should compare other music players on the market.
There isn't really one inherently; a music player like foobar2000 only takes a few MB of memory even with many plugins. That doesn't mean Clementine and Winamp haven't found ways to waste resources that aren't loading a full Chromium instance (after all, Chromium is pretty efficient considering what it actually brings to the table.)
As a matter of fact(but not scientifically accurate), chromium-based browsers were consuming twice as much RAM on Win than on Linux whenever I checked.