I didn't state that all inverters sound the same. I said that the Powerwall with my system has no sound. If you read what I wrote, I have pointed out that inverters are effectively large switch mode power supplies and people are just blindly promoting them without any idea of the noise profile. You, based on your friend, have made a ton of conclusions and promoted the Giandel as "great" when you have no idea of the distortion spectrum, or the noise spectrum and how that will behave with the vast majority of audio electronics out there. I have pointed out, quite correctly, that pure since wave has no technical advantage in terms of reducing the noise of audio power supplies or improving how they operate. Sine waves are simply what we must live with due to the nature of rotating machinery as our primary power generation methodology.
You also assume that one must have user reports of a specific inverter to have any meaning. Fortunately, there are engineers that don't have to work under your limitations.