Yeah, it does. They didn’t do the best job with it, but it does actually support HDR displays.
It’s mostly taking a while on PC because Windows itself doesn’t support HDR, and I remember reading somewhere that in order for DirectX to output HDR it needs to be in exclusive fullscreen mode for some reason. It’s super early on in HDR’s life right now, we may not end up seeing proper HDR support until the actual HDR monitors like the ASUS PG27UQ comes out later this year.