Hi Robin, I agree BS.2051-3 is too wide, e.g. allowing for too steep top layer elevations, but at least it’s something to compare arbitrary, virtual processors against. From an “immersive” quality/monitoring perspective, I think only an ideal setup is relevant, i.e. equidistant with limited reproduction room contribution.
I’m with you on open format as well, ideally backed by AES, Japanese, Chinese, EBU and other pro institutions.