Everything that's in a rear speaker is also in the corresponding front speaker, just at a lower volume - there's nothing unique (or "discrete" as we call it here) to the rear speakers. It doesn't make the mix bad, or weak, it just reduces the surround effect. To me it makes the soundfield sound more like it's about 270 degrees, ie there's nothing in the 90 degrees behind the listener, and the most aggressively panned elements sound more like they're at the extreme 'sides' of the soundfield, ie in line or just behind your earholes. If they'd simply made all these elements 100% "rear discrete" I think this would basically be a perfect mix. Tonality-wise, it's so much more pleasurable to listen to than any of the previous incarnations (and I've owned them all, original LP, quad LP, quad 8 track, original CD, etc.) of the album that the shortcomings in the mixing decisions aren't enough to make me choose another version.
I think I've heard every version of this album in stereo - original LP, original CD, remastered CD, MoFi SACD, etc. and in a nutshell, the original mix is a turd, and even MoFi couldn't polish it. It's a midrange mess (you should see a frequency analysis, it basically looks like mount everest with it's peak around 2.5kHz) and remixing it is/was the only way to fix it.
My preferred stereo version is the Paul Klingberg remix from the 2002 DVD-A, done at the same time as the 5.1 remix. The best version of this mix is available as a 24/96 download from HDTracks and other similar sites - the version on the DVD-A had some compression applied (I think it was in the DR8 region) whereas the HDTracks version is (seemingly) uncompressed and clocks in at DR11.
I say that with the caveat that the Klingberg remix of II isn't entirely historically reverential, but it just sounds so much better than the original mix, and allows the excitement of the original performances to shine through so much more. The Steven Wilson remix does a much better job of capturing the nuances of the original mix, but that includes being beholden (for the most part) to the original midrangey tonality of the original mix, when I think he could've taken the small liberty of flattening it out a bit. The result is you get a mix that sounds a lot like the original, just with a layer of grunge removed.