I think you're misinterpreting that. What it is saying is that if you set the line-out to "pass-through", rather than "line-level", you'll be able to control the volume of the sound using the app, which will change what is being fed to your amp. It's not actually adjusting the volume of your amp, just the data being fed to it.
By the way, here's a list:
Where did you find this list.Anyone an insight on the support by Sony receivers?
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