The new 4K UI Setting that you can toggle on or off, has nothing to do with the new font for character names, npcs, targetable objects etc.

There is also no toggle for this font change, you can only currently "fix" this by reverting to DX9. Which I feel is unnecessary for something so simple as this.

I'm not downplaying it's importance though, you literally have to look at the font all the time during play. And while my eyes have adjusted to it a bit better now, there are clear times where it just looks plain ugly and flickers/distorts when moving closer or further away from an object. Also the readability can become poor depending on the colour of the text vs. a light background.