They are exact specs for proper distance to screen size. While some may not personally like what the specs say, it is still the proper field of vision the images are shot and edited for.
The reality within the various posting banter and conflicting information is that in the end - there are no "exact specs" other than math computations - viewing is about the human interaction of visual presentations.
People's vision, hearing, and the environment (things like ambient light, brightness, contrast, color depth, screen reflection and angles, acoustics, etc.) all vary. Math can be used to compensate for variables...no doubt.
Why there may be preferred, recommended, and "in a perfect world that doesn't exist suggestions" for specifications...in the end..."your mileage may vary" is most appropriate.
Having significantly invested in 2 different certified
sound and visual and audio engineers in the planning, design, implementation, configuration, and final "alignment and tuning" of a 6-figure THX-certified, rack-mounted 116" projection dedicated Home Theater, I appreciate and understand the value of these things better than most folks based upon real-world experience. Four (4) different high-end calibration devices were used to peak the video and audio. Both engineers, using different equipment at different times, agreed upon the final results. Thereafter, 2 adjustments were made - 1 audio and 1 video to suit viewer preferences.
All that said, while there is plenty of science in how the viewing experience can be optimized...personal taste (which may or may not "see or hear" things the same way) always trumps it in the end.
Circulating back to the topic at hand - 4K HDTV....if last year was any indication of what we'll see and hear from manufacturers in < 2 weeks at CES...there are some best practices, standards, and common traits already forming that will impact how it is delivered and viewed.
A number of us will be honing in on vendor booths to get the latest info on this topic - from advance indications, there will be more than 18 manufacturers representing 4K HDTV brands. Based on past years, there will likely be reports at DBSTalk about information learned onsite.