Even a rough version of the deformable mirror AR VRD described by researchers at UNC Chapel Hill [1] accomplishes 100 degrees FOV with accommodation.
They went further with the Pinlight achieving 110 in 2014 [2]
The technical limit according to our own work for VRD FOV is H: 200o, V: 140o (Combined). So either they're ignoring work in the field intentionally cause they don't want to do VRD or they don't know about it. My guess would be the former.
[1]http://telepresence.web.unc.edu/research/dynamic-focus-augme...
[2]http://www.cs.unc.edu/%7Emaimone/media/pinlights_siggraph_20...
edit: I find this whole thing extremely frustrating. Facebook could throw 2 billion dollars at VRD tech and actually get to a working stable consumer grade system if they wanted to - everything is there for it. Why aren't they?