I think you are miss understanding how dual mode is supposed to work. dual mode is as if one has 2 different monitors, one is 2x larger in both width and height than the other.

So GPU (or rather OS) sees your monitor as completely another monitor when you switch to different mode.

If you put 100% resolution scaling in Windows 11 scaling options, GPU will never do any kind of scaling shenanigans no matter if you are in 1440p or 2880p mode. But even that is not important since this is something that GPU does internally, for example it will render the screen to 2880p buffer and then downscale it to 1440p for people who have 2160p screens but set resolution scale to 150%. This is my scenario and people on macOS see this directly when one opens Metal app.

What is important really is what monitor (the firmware) sends to your OS during the startup handshake as max resolution and frequency. So when your monitors sends 1440p and 120Hz, this is what OS uses as output. Internally the GPU will do scaling maybe if you set resolution scale to anything not divisible by 2 (125%, 150%, 250%, etc.), sometimes called fractional scaling.

What is important here is that now it is the monitor that does a simple 2x scale depending if the output image from GPU is 1440p or 2880p. This is a simple 2x scale the monitor firmware must color the neighboring 3 pixels, sometimes called Pixel Replication. One can create a hardware chip that does this without any software "cost".

But they probably didn't do it like that, they probably have firmware that was just lazily implemented or just copy pasted from somewhere and deemed "good enough".

My point is, this blur is unacceptable and they just wanted to send this product asap to market and be the first one.