I still can't understand how this idea persists. It isn't that the listener perceives a drooping frequency response as natural: it's that the listener separates the direct sound from the reverberant, thereby hearing the speaker's flat, neutral frequency response. The reverberation that the microphone and dumb Fourier transform cannot separate from the direct signal is what produces the downward response in the in-room measurement. The precise drooping frequency response is the result of playing a neutral speaker in a certain type of room; it is meaningless as a target in a different type of room or with a different type of speaker.
The conventional explanation is messy, has to refer to a 'mystery' and is basically talking about 'the wrong thing'. The other explanation is neat, clear, precise, elegant and explains why a genuinely neutral speaker sounds neutral without resorting to 'room correction', and why it produces the downard slope in a real room. What's not to like? Answer: it means that hearing is more capable than just a frequency response analyser, and renders the entire hobby/industry of room correction as null and void.