The only confusion is understanding manufacturer's advertising gimmick spec methods.
720p is the so to speak beginnings of HD spec (sort of or at least once redefined as hd refering to 16:9) & is 1k which folks often mistakenly think 1080p is.
Again we like naming schemes.
As you know with computers prior we describe displays on the pc side with "?GA" which represented Res & number of colors (primarily) put a "W" in front of the "?GA" & now you have widescreen.
So HD now represents tv standard of 16:9
720p HD (1280*720) 1K (True)
1080p FHD (1980*1080) 2K (Less)
1440p QHD (2560*1440) 2.5K (True)
2160p UHD (3840*2160) 4K (Less)
4320p UHD (7680*4320) 8K (Considerably Less)
With using the HD naming scheme as accepted today the above is true for "k" hd displays.
True K display would be 1:1 others are less.
So similarily a new standard of letters could be introduced for a special purpose displays.
Oculus/Vive 2.1k*1.2k. (FHDVR)
PiMax BE. 2.5k*1.4k. (QHDVR)
PiMax 4k. 3.8k*2.1k (4kHDVR)
PiMax 5k. 5.3k*1.4k (5kUWVR)
PiMax 8k. 7.6k*2.1k (8kUWVR)
We have some standardization in VR
k= Width in pixels rounded up...
xF = Fov (x is S/W/U)
-S = Standard 90 to 110
-W = Wide >110 to 160
-U = Ultra Wide >160 to 200
yR= Reality (y is A/M/V)
-A = Augmented
-M = Mixed (MS)
-V = Virtual
We now have a marketable basic spec standard.