IMO,
The equilateral triangle holographic effect is a recording phenomenon, nothing really to do with live-music reproduction , best to tune your setup to the effect that suits you best , for some its straight ahead no toe for others only massive toe in will suffice..
certainly agree that aspects of the potential holographic phenomenon of stereo are not like the live experience. OTOH optimizing the holographic aspect of stereo brings along with it many other benefits.
first; your stereo reproduction goal should be to reproduce the truth of the recording; which will resemble the 'live' experience to varying degrees. and everything you do with your electronics, signal path, room set-up, acoustical treatments, power grid, shelves, footers, and bass linearity is all serving that end. the listening position is one of the more dominant aspects of your presentation so it's optimization is very important. maybe your personal sonic priorities place holographic imaging down the list. but still when that gets optimized everything else has to be right too.
personally I find that as I reduce distortion in the system in various ways I get more separation between various musical themes and more clear rendering and articulation of bass and dynamics, and more clarity on peaks. all these things also contribute to bettering the holographic presentation. not that that issue is the specific goal in and of itself, only that it's evidence of progress in performance.
lastly; speakers disappearing is at the heart of hearing the recording and not the room and reproduction chain. the greater the holographic nature of the presentation, the more your speakers are disappearing. so if a listening position has a greater ability to allow the speakers to disappear then that is positive.
will sitting at the tip of the equilateral triangle
always optimize holographic rendering? so far it has in my experience, but I don't know that it always works that way.
Best to experiment with what works for you and your room, their here or you are there kind of experience .
Regards
there is no wrong approach to this issue; only that the more one understands choices and cause and effect the better one is equipped to optimize for their own tastes. and sometimes until you actually hear what is possible your mind can be a bit closed.