In regard to HDR:
nVidia's older v1 G-SYNC module is limited to 3440x1440@120Hz. Even if a 3440x1440 G-SYNC monitor includes a panel that can reach beyond 120 Hz, the v1 G-SYNC module will limit the monitor to 120 Hz regardless (see 34GK950G).
It follows that 3840x1600@144Hz (as supported by the 38GL950G) is beyond the capabilities of the v1 G-SYNC module, meaning this monitor will ship with the newer v2 G-SYNC module. The v2 G-SYNC module supports HDR (or more precisely, the v2 G-SYNC module supports the HDR10 protocol).
If a monitor combines a newer panel with a HDR10 capable controller, then nothing prevents the manufacturer from at least slapping a DisplayHDR 400 badge on it. Combining this panel with the v2 G-SYNC module already provides LG with everything that is necessary to achieve that HDR certification level and it does so without LG having to invest a penny more into engineering.
Two assumptions:
- nVidia doesn't release an entirely new revision of their v1 DP1.2 G-SYNC module that supports 3840x1600@144Hz (in theory DP1.2 does provide enough bandwidth to drive that resolution and refresh rate, but DP1.2 doesn't support HDR10).
- LG won't pass up, for no reason, on the marketing opportunity to slap a HDR badge on any monitor that deserves it.
Without a FALD backlight a DisplayHDR 1000 certification is off the table. LG might go with a DisplayHDR 600 or 400 certification, or forgo the official VESA certifications entirely and just slap their own "HDR capable" badge on it. If the above two assumptions are true, then LG is practically guaranteed to go with one of those options. That this monitor, with a v2 G-SYNC module, isn't at least marketed as "HDR capable" is almost unthinkable.
Of course DisplayHDR 400 shouldn't be taken seriously. Even DisplayHDR 600 barely deserves to be called HDR, but that is a different topic.