1. The research and consensus seems to be that. Here is a sampling.
AES Paper: FULLY AUTOMATIC LOUDSPEAKER-ROOM ADAPTATION – the RoomPerfect system
JAN ABILDGAARD PEDERSEN1 AND KASPER THOMSEN2
"Reproduction of sound in a room always results in an increased sound pressure level towards lower frequencies. This is partly a consequence of the lower absorption found in typical rooms at low frequencies. However this is natural to the human ear as this provides the sense of being in a room. Consequently a room correction system cannot be allowed to remove this smooth increase in level at low frequencies, also referred to as the room gain [32, 33]."
AES Paper: ADJUSTING A LOUDSPEAKER TO ITS ACOUSTIC ENVIRONMENT - the ABC system
Jan Abildgaard Pedersen
Acoustics Research, Bang & Olufsen, Struer, DK-7600, Denmark, e-mail: firstname.lastname@example.org
"Another problem of such systems is the choice of a suitable target function, e.g. a constant amplitude characteristic has been found not to be optimal. "
Presentation by Earl Geddes: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CDwQFjAB&url=http%3A%2F%2Fwww.gedlee.com%2Fdownloads%2FOptimalBassPlaybackinSmallRooms.pptx&ei=rUxgUYfzBeftiQKnqoCoDw&usg=AFQjCNGFlHGd1VRRrHGVd9pchJBd_ZIRbg&sig2=D460C5iYDq9R9e-f_Uhptw
[*] Good bass, in the context of this report, and my personal preference, is a frequency response that has a subtle rise to the lowest frequencies, but which is otherwise very smooth in both frequency and space
[*] Why the “subtle rise”? Why not just flat?
[*] The reason is that the bass in small rooms is always “dead” when compared o larger spaces
[*] Hence a flat response will sound lacking in bass because there is a tradeoff between the sensation of level and the duration of a signal – the shorter signal will sound softer
[*] How much “bass enhancement”?
[*] I have found that between 3 and 6 dB of bass boost from about 200 Hz down to about 20 Hz is what I judge to be “neutral”
[*] There are those who judge bass by its level despite the fact that this level is not at all natural or neutral
[*] This is not what this discussion is about
[*] This discussion is about “neutral, but adequate bass reproduction in a small room”
Here is a graph showing target curve from B&K (the gods of measurement mics and such) showing the target curve should be, dating back many decades:
Here is a less formal reference but with a nice picture: http://www.hifizine.com/2011/06/bass-integration-guide-part-1/
2. Formal listening tests say so as I quoted. These were performed double blind. The listener heard some tracks and was asked to judge is performance in various areas including bass. Here is a sampling from this AES report: The Subjective and Objective Evaluation of Room Correction Products
Sean E. Olive, John Jackson, Allan Devantier, David Hunt and Sean M. Hess, Harman International,
"The more preferred room corrections (RC1-RC3) produced smoother curves with more extended output below 60 Hz. The slope of the curve also seems to be an important indicator of preference: The more preferred room corrections had more downward sloped curves, whereas the least preferred room corrections (RC5 and RC6,) tended to have flatter slopes, probably related to the manufacturer’s choice of target curve."
As to the FUD campaign against this research, the only thing that matters is if you can specify an actual fault on how human subjects were all gamed in a double blind test to say they like more bass. The mere implication doesn't amount to anything I am afraid especially when the listening tests confirmed what is known as proper target curve per above references. Note that another competing non-Harman did well by using the same technique as did doing no EQ at all! The correlation was very high across all the systems in this area as evidenced by consensus across 6 expert listeners.
3. The science indicates so. When the wavelength of sound becomes large with respect to the source and distance to barriers, the sound power accumulates with respect to each barrier presented (so called "room gain."). This only happens in low frequencies. Now add to this the fact that in our typical living environments we have many furnishings that absorb mid to high frequencies but almost nothing that absorbs sub frequencies. Put succinctly, what we think is "real," that is, how everything sounds to us in everyday life, is subjected to room gain. Taking it out would mean presenting a situation that is not natural. So not surprising that both industry/research consensus and listening tests confirm the same.
4. My own testing. I have had the pleasure of owning programmable/customization EQ systems for a decade now. Using these systems, one can easily play with a single domain like low frequency optimization down to even a single filter/mode correction. Try as I have, I cannot make myself like a flat bass response. Yes, qualitatively it sounds proper flat. But I am always compelled to boost the level post equalization. I suggested a set of tests for people to run to confirm the same. While Audyssey is an all or nothing proposition making such test harder, you can get there by only listening to the sub.
And this graph from that post in survey of professional recording/mixing rooms:
Net, net, what you are saying is a dream. There is no such reference in audio. Never has been and never will be. And further, professionals are no better situated than you and I are in determining "what is right." So they fiddle with their rooms just the same per above graph.
So the only plan is to close your eyes and test your own systems and determine your preferences. If you can't do that, then the starting point should be what all of the above evidence says, not just some gut feeling that flat is right backed by IMHO a mistaken target curve in mass market AVRs.