I also looked for it, but only a mention here and there in the forum.
Probably just an update made available through PiTool (which would mean a stable release) which haven’t made it to the website or You, yet)… 
EDIT:
I’ll check in PiTool now… 
EDIT2:
EDIT3 (after update):
EDIT4 (new firmware too):
EDIT5: Seems we have 140 degrees FoV on 144Hz on the 5K+:
hmdq version 1.3.2 - collecting OpenVR headset characteristics in no time
Time stamp: 2020-05-20 22:52:47
hmdq version: 1.3.2
Output version: 4
OS version: 10.0.18362.836
OpenVR runtime: C:\Program Files (x86)\Steam\steamapps\common\SteamVR
OpenVR version: 1.11.13Device enumeration:
Found dev: id=0, class=1, name=HMD[0:HMD]
1000 : TrackingSystemName = “aapvr”
1001 : ModelNumber = “Pimax 5K Plus”
1002 : SerialNumber = “<random_number>”
1003 : RenderModelName = “generic_hmd”
1005 : ManufacturerName = “Pimax VR, Inc.”
2002 : DisplayFrequency = 143.998Recommended render target size: {3004, 2632}
Left eye HAM mesh:
original vertices: 120, triangles: 40
mesh area: 19.11 %Left eye head FOV:
left: -70.22 deg
right: 40.01 deg
bottom: -49.73 deg
top: 49.73 deg
horiz.: 110.24 deg
vert.: 99.45 degRight eye HAM mesh:
original vertices: 120, triangles: 40
mesh area: 19.11 %Right eye head FOV:
left: -40.01 deg
right: 70.22 deg
bottom: -49.73 deg
top: 49.73 deg
horiz.: 110.24 deg
vert.: 99.45 degTotal FOV:
horizontal: 140.45 deg
vertical: 99.45 deg
diagonal: 137.89 deg
overlap: 80.03 degView geometry:
left panel rotation: 0.0 deg
right panel rotation: 0.0 deg
reported IPD: 64.1 mm
That’s new, right?
EDIT6: Also shown in PiTool (though “normal” could mean “a new normal” if not backed by hmdq output):
EDIT7: My unit is a 203600* model from Week 2, 2019.