but it’s rather silly if you understand the room to be over 50% of the sound from a pair of speakers. And if you doubt that figure, set up the hifi in the garage or basement.
I would honestly say this is conservative. I've measured rooms, and with +- 20 dB nulls and peaks, a room can have tremendous effects on the output power in the bass, the timber, and the ability to resolve spacial cues.
It is also true that we can train our ears to reduce some of these effects. Try recording a person's voice, or just your stereo in a room, then listen to it with headphones. You'll be amazed. With training, you can teach yourself to stop blocking this, and you suddenly can hear the room itself.
Best,
E