Since launch, i've never seen any of the developers comment on this. Which is quite frustrating to say the least.
Here you go: So far we don't have any downscaling of the HUD at all. However, on 4K displays we are by default scaling up the HUD by 2x, and the option is just setting the scale back to 1x.
Not trying to say this means we can't add the scale for normal resolutions, just want to highlight that it is a slightly different thing. =)