"4K textures" aren't textures for 4K screens. It's just a size of 4096x4096.
There are instances where those texture numbers will correlate with the screen like UI elements.
But in general, that's not true. If you zoom in on an object, you might only see 1/8th of it, so you're only seeing 1024x2048.
The idea of '4K assets' is largely a misnomer.
Many games don't have different sets of assets for the resolution. Xbox Series games might in some cases, but it's not the norm. Other consoles don't do that, and PC tends to have texture quality as a separate setting from resolution, because they don't have to correlate.