It helps to have some context. If you read Toole's book on this point he comments that the industry as a whole tends to misunderstand the role of reflections. Both studios and home listening rooms suffer given that the intent of treatment tends to be the elimination of indirect sound to one extent or another, with approaches like the reflection free zone, the nonenvironment room, live end/dead end. These approaches are based largely on physical measurements of room acoustics (frequency response, reverb time, noise) with incomplete psychoacoustical considerations.
Toole's book and commentary on studio designs is in effect a "Circle of Confusion" unto itself - as so many i've interacted with seem to draw their "understanding of studio design" solely from Toole's commentary alone - when Toole's book(s) are not authoritative sources on studio design. and thus we see erroneous, misleading, and incomplete statements like that made above.
Live End Dead End, and by nature Reflection Free Zone (Peter D'Antontio's geometric approach to achieving the LEDE psycho-acoustic response) - in no way "eliminates indirect sound". they attenuate and delay the indirect specular sound-field such that it can be managed and
reintroduced to the listening position at a later time, as a certain type, and from certain directions.
LEDE/RFZ create an effectively anechoic time period (ISD-gap) where-by no indirect room contributions (indirect specular reflections) are allowed to impede the listening position. ie, no high-gain sparse (focused) specular reflections are allowed that would skew accuracy of the direct signal with respect to localization, imaging, and speech intelligibility. this ISD-gap time-length in effect defines the perceived psycho-acoustic size of the bounded space, and is done so to be 2-5ms longer than the ISD of the tracking room (which allows the operator to hear the recording room indirect reflections/sound-field prior to any indirect reflections from within the control room masking on top). however in no way does this anechoic response completely extend infinitely (ie, the erroneous statement that they "eliminate the indirect sound"). instead, a REFLECTION-RICH indirect sound-field is eventually re-introduced to the listening position, being no more than -12dB down from direct signal, by nature of broadband 1-dimensional reflection phase grating diffusers on the rear/rear-side walls with the wells oriented vertically which provide the diffraction lobes in the horizontal plane. this provides a reflection-rich, dense, exponentially-decaying,
laterally-arriving indirect sound-field for passive envelopment (emulating the natural reverberant sound-field that develops in Large Acoustical Spaces). the diffuse indirect sound-field creates MORE reflections with MORE closely spaced comb-filters to minimize the frequency-response anomolies as one moves about the room.
so in no way do these studio models aim to "eliminate indirect sound" - they simply manage it appropriately and delay and subsequently reintroduce it back to the listening position at a later, defined time and in a well-defined manner to achieve specific, pscyho-acoustic triggers on to the ear/brain system. and in effect, the "studio design indirect sound field" contains a significantly more "reflection-rich" response than an untreated room would.
only Non-Environment in effect "eliminates indirect sound" entirely (ie, an anechoic speaker-listener response) - but in no way is the room itself anechoic or lacking of indirect sound-field as experienced from the operator's perspective.
the fact you refer to these studio designs as "incomplete psychoacoustical considerations" is bewildering. LEDE is literally a psycho-acoustic response to achieve accurate direct signal as perceived at the listening position while hearing in totality the first indirect contributions from the recording room. the design has literally evolved with further understanding of psycho-acoustic effects as well as being put into practice by nature of how well mixes translate to a myriad of other rooms and system. it provides a non-destructive sense of the room, and allows more-even indirect sound field (minimizing frequency response variations) as one moves about the room (ie, a much larger "sweet spot").
with approaches like the reflection free zone, live end/dead end. These approaches are based largely on physical measurements of room acoustics (frequency response, reverb time, noise) with incomplete psychoacoustical considerations.
this is wildly inaccurate and misguided. LEDE/RFZ focus heavily on time-domain response and is entirely validated and thus certified via the Envelope Time Curve (ETC) response.
The net effect for consumers is that most companies offering treatment imitate these approaches and, due to a lot of factors, not the least of which is practicality, their products are usually based on broadband absorption (foam, mineral wool, fibreglass cores with questionable coverings) and are very thin (1 or 2 inches). These panels are increasingly less effective as you move down in frequency, rapidly dropping off in absorption below around 100Hz or 200Hz, depending on thickness. That slope in effective absorption modifies the spectral content of all indirect and reflected sound, which is more important than you'd think, besides showing inadequacy of the product.
a case of operator error. the modeling, behavior, etc of porous absorbers is well understood. if a user is deploying 1-2in porous absorbers an in effect creates a low pass filter (coloring or "eq'ing" the reflection instead of attenuating it entirely via the use of broadband, sufficiently thick treatments) - then that is simply user error and has nothing to do with studio design.
why would you bring light to a method of doing something wrong? it has no bearing on the actual design and criteria of which these studio models define.