[maeln]

They specifically mention that one of the advantage for them is the loudness management, to avoid having video with widely different range when their user are scrolling through their timeline.

I think Opus also has loudness management, but they seem fairly specific about the one that xHE-AAC provide : > Instead of burning in a specific target level and dynamic range compression (DRC) profile during encoding, xHE-AAC allows us to leave the original audio characteristics untouched and delegate loudness management processing to the client via loudness metadata, for the optimal audio experience based on context.

So maybe the xHE-AAC does provide a tangible benefit in this department.