Sounds to me like that article is dealing more with multichannel music reproduction than for HT going by this statement:
"It is worth noting that the ITU (International Telecommunications Union) has recommended that the rear speakers be positioned more to the side of the listener, angled between 100° and 120°. (See section 1.) This recommendation, which was originally developed for television broadcast and not for music,
represents a compromise between envelopment, which is strongest at 90°, and rear phantom imaging, which improves as the rear speakers are moved further back and are angled in more steeply. Although this practice has been adopted by many surround professionals in the film and broadcast industries, it may not
be suitable for music applications where the rear speakers are used to carry vital musical information and not just ambience or effects. Speaker placement, therefore, need not be restricted to the ITU recommendation alone: at the engineer’s discretion, more extreme rear speaker anglings (at up to 150°) are acceptable, depending upon the program content being mixed."
It also states that in the home market speaker placements can be all over the place and this article is just for the use in the mixing of sound at the professional level to provide something of a standard. I also noted it is now a 6 yr old document. I wonder if anything has changed.
